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PHP, che significa "PHP: Hypertext Preprocessor", è un linguaggio di scripting general-purpose Open Source molto utilizzato, è specialmente indicato per lo sviluppo Web e può essere integrato nell'HTML. La sua sintassi è basata su quella di C, Java e Perl, ed è molto semplice da imparare. L'obiettivo principale del linguaggio è quello di permettere agli sviluppatori web di scrivere velocemente pagine web dinamiche, ma con PHP si possono fare molte altre cose.
Questo manuale consiste principalmente in un elenco commentato di funzioni, ma contiene anche una guida al linguaggio, la spiegazione di alcune delle principali caratteristiche e altre informazioni aggiuntive.
Il manuale è fornito in diversi formati qui: » http://www.php.net/download-docs.php. Maggiori informazioni su come questo manuale viene sviluppato possono essere trovate nell'appendice 'Informazioni sul Manuale'. Se si è interessati alla storia del PHP, leggere l'appendice.
Evidenziamo le persone attualmente più attive sulla prima pagina del manuale, ma ci sono molti altri contributori che ci aiutano nel nostro lavoro o che hanno dato un grande aiuto al progetto nel passato. C'è un gran numero di persone non citate che aiutano con le loro annotazioni sulle pagine del manuale, le quali vengono continuamente incluse nei riferimenti; siamo molto grati di questo lavoro. Tutte le liste qui sotto sono in ordine alfaberico.
I seguenti contributori devono essere riconosciuti per l'impatto che hanno avuto o continuano a dare aggiungendo contenuti al manuale: Bill Abt, Jouni Ahto, Alexander Aulbach, Daniel Beckham, Stig Bakken, Jesus M. Castagnetto, Ron Chmara, Sean Coates, John Coggeshall, Simone Cortesi, Markus Fischer, Wez Furlong, Sara Golemon, Rui Hirokawa, Brad House, Pierre-Alain Joye, Etienne Kneuss, Moriyoshi Koizumi, Rasmus Lerdorf, Andrew Lindeman, Stanislav Malyshev, Rafael Martinez, Rick McGuire, Yasuo Ohgaki, Derick Rethans, Rob Richards, Sander Roobol, Egon Schmid, Thomas Schoefbeck, Sascha Schumann, Dan Scott, Masahiro Takagi, Michael Wallner, Lars Torben Wilson, Jim Winstead, Jeroen van Wolffelaar e Andrei Zmievski.
I seguenti contributori hanno effettuato un significativo lavoro redigendo il manuale: Stig Bakken, Gabor Hojtsy, Hartmut Holzgraefe e Egon Schmid.
I mantenitori attualmente più attivi sono: Friedhelm Betz, Etienne Kneuss, Nuno Lopes, Hannes Magnusson, Felipe Pena e Maciek Sokolewicz.
Anche queste persone si sono impegnate a gestire le note utente: Mehdi Achour, Daniel Beckham, Friedhelm Betz, Victor Boivie, Jesus M. Castagnetto, Nicolas Chaillan, Ron Chmara, Sean Coates, James Cox, Vincent Gevers, Sara Golemon, Zak Greant, Szabolcs Heilig, Oliver Hinckel, Hartmut Holzgraefe, Rasmus Lerdorf, Matthew Li, Andrew Lindeman, Aidan Lister, Maxim Maletsky, Bobby Matthis, James Moore, Philip Olson, Sebastian Picklum, Derick Rethans, Sander Roobol, Damien Seguy, Jason Sheets, Tom Sommer, Jani Taskinen, Yasuo Ohgaki, Jakub Vrana, Lars Torben Wilson, Jim Winstead, Jared Wyles e Jeroen van Wolffelaar.
PHP (acronimo ricorsivo per "PHP: Hypertext Preprocessor") è un linguaggio di scripting general-purpose Open Source molto utilizzato, è specialmente indicato per lo sviluppo Web e può essere integrato nell'HTML.
Risposta banale, ma che cosa significa? Un esempio:
Example #1 Un esempio introduttivo
<html>
<head>
<title>Esempio</title>
</head>
<body>
<?php
echo "Ciao, sono uno script PHP!";
?>
</body>
</html>
Notate come questo esempio è differente da uno script scritto in altri linguaggi tipo Perl o C -- invece di scrivere un programma con parecchi comandi per produrre HTML, si scrive in HTML con qualche comando immerso per ottenere dei risultati (in questo semplice esempio, la visualizzazione di una frase). Il codice PHP è delimitato da speciali start ed end tag che ne indicano l'inizio e la fine e che consentono di passare dal modo HTML al modo PHP.
Ciò che distingue PHP da altri linguaggi di scripting del tipo client-side JavaScript è che il codice viene eseguito nel server. Per avere uno script simile a quello sopra nel vostro server, il client dovrebbe ricevere il risultato ottenuto con lo script, senza sapere mai quali sono le funzioni eseguite. Potete persino configurare il vostro web server per processare tutte i vostri file HTML con PHP ed allora non ci sarebbe realmente alcun modo per gli utenti di sapere cosa avete sul vostro server.
La cosa più interessante nell'uso di PHP è che si tratta di un linguaggio estremamente semplice per il neofita, ma che, tuttavia, offre molte prestazioni avanzate al programmatore di professione. Non lasciatevi impressionare dalla lunga lista delle potenzialità di PHP. In poco tempo potrete iniziare a creare velocemente semplici scripts.
Sebbene lo sviluppo di PHP abbia come obiettivo lo scripting server-side, si può fare molto di più con esso. Leggete, e consultate la sezione Che cosa può fare PHP? oppure andate su tutorial introduttivo se si è interessati solo alla programmazione web.
Qualsiasi cosa. PHP ha come obiettivo principale lo scripting server-side, per cui può fare tutto ciò che può fare un qualunque programma CGI, come raccogliere dati da un form, generare pagine dai contenuti dinamici, oppure mandare e ricevere cookies. Ma PHP può fare molto di più.
Esistono tre campi principali in cui vengono usati gli scripts PHP.
PHP può essere usato su tutti i principali sistemi operativi, inclusi Linux, molte varianti di Unix (compresi HP-UX, Solaris e OpenBSD), Microsoft Windows, MacOS X, MacOS Xserver, RISC OS, e probabilmente altri. Inoltre supporta anche la maggior parte dei server web esistenti. Ciò comprende Apache, Microsoft Internet Information Server, Personal Web Server, i servers Netscape ed iPlanet, Oreilly Website Pro server, Caudium, Xitami, OmniHTTPd, e molti altri. Per la maggioranza dei servers PHP ha un modulo, per gli altri che supportano lo standard CGI, può funzionare come un processore CGI.
Pertanto, con PHP si ha la libertà di scegliere praticamente qualsiasi sistema operativo e qualsiasi server web. Inoltre, si può anche scegliere se fare uso di una programmazione procedurale oppure orientata agli oggetti, o una combinazione di entrambe. Sebbene non tutte le caratteristiche standard di OOP siano realizzate in PHP 4, molte librerie di codice e grandi applicazioni (compresa PEAR library) sono state scritte usando codice OOP. Con la version 5, il PHP supera le debolezze dell'OOP presenti in PHP 4, ed introduce in modo completo il modello a oggetti.
Con PHP non siete limitati soltanto ad un output in HTML. Le possibilità di PHP, infatti, includono l'abilità di generare immagini, files PDF e perfino filmati Flash al volo (utilizzando libswf e Ming). Sarete in grado di generare facilmente qualsiasi testo, come XHTML e qualsiasi altro file XML. PHP può autogenerare questi file, e salvarli nel file system, piuttosto che eseguire un printing esterno, o creare server-side cache per contenuti dinamici.
Una delle caratteristiche più importanti e significative di PHP è la possibilità di supportare una completa gamma di databases. Scrivere una pagina web collegata ad un database è incredibilmente semplice. Attualmente sono supportati i seguenti database:
Esiste anche un'estensione database abstraction extension (chiamata PDO, che vi permette di usare in modo trasparente qualsiasi database da essa supportato. Inoltre PHP supporta ODBC, lo standard di collegamento con i database, pertanto è possibile collegarsi con qualsiasi database che supporti questo standard mondiale.
- Adabas D
- dBase
- Empress
- FilePro (read-only)
- Hyperwave
- IBM DB2
- Informix
- Ingres
- InterBase
- FrontBase
- mSQL
- Direct MS-SQL
- MySQL
- ODBC
- Oracle (OCI7 and OCI8)
- Ovrimos
- PostgreSQL
- SQLite
- Solid
- Sybase
- Velocis
- Unix dbm
PHP fa anche da supporto per dialogare con altri servizi utilizzando i protocolli del tipo LDAP, IMAP, SNMP, NNTP, POP3, HTTP, COM (in Windows) e innumerevoli altri. Potete anche aprire network sockets ed interagire usando qualsiasi altro protocollo. Inoltre supporta l'interscambio di dati complessi WDDX tra, virtualmente, tutti i linguaggi di programmazione web. A proposito di interconessioni, PHP supporta l'installazione dei JavaObjects e l'utilizzo di questi come oggetti PHP in modo trasparente. Si può anche usare la nostra estensione CORBA per accedere ad oggetti remoti.
PHP possiede alcune caratteristiche molto utili per la gestione del testo, da POSIX Extended o Perl regular expressions al parsing di documenti XML. Per fare il parsing ed accedere ai documenti XML, il PHP 4 supporta gli standard SAX e DOM, e si può utilizzare il modulo XSLT per le trasformazioni dei documenti XML. Il PHP 5 standardizza tutte le estensioni XML sulla base solida di libxml2 ed espande le caratteristiche aggiungendo SimpleXML ed XMLReader.
L'ultimo, ma di non poca importanza, PHP ha molte altre estensioni interessanti, come funzioni per motori di ricerca mnoGoSearch, le funzioni IRC Gateway, molte utilità di compressione (gzip, bz2), conversione dei calendari, traduzione...
Come si può notare, questa pagina non è sufficiente per elencare tutte le funzioni che PHP offre. Per approfondire il discorso sulle suddette caratteristiche, consultate le sezioni Installazione di PHP, e function reference
Di seguito, in una breve e semplice introduzione, vorremmo mostrare alcuni esempi per l'utilizzo di PHP. Essi sono relativi soltanto alla creazione dinamica di pagine web, anche se PHP non ha funzionalità limitate esclusivamente alla creazione delle sole pagine web. Fare riferimento alla sezione intitolata Cosa può fare PHP per avere ulteriori informazioni.
Le pagine web create con PHP vengono trattate come normali pagine HTML e possono essere create e modificate nello stesso modo in cui si sviluppano normali pagine HTML.
In questo tutorial assumiamo che il vostro server abbia il suporto PHP attivato e che tutti i file con estensione .php vengano gestiti da questo. Quasi in tutti i server questa è l'estensione di default per i file PHP., ma consultatevi col vostro system administrator per sicurezza. Se il vostro server supporta PHP, allora, non è necessario fare nulla. Semplicemente create i vostri file .php e scaricateli nella vostra directory web, il server le analizzerà e le eseguirà magicamente. Non è necessario compilare nulla nè installare strumenti aggiuntivi. Si pensi ai file PHP come a dei semplici file HTML con una intera famiglia aggiuntiva di magici tags che consentono di fare ogni sorta di cose.
Creare un file con nome ciao.php nella directory del web server che abbia il seguente contenuto:
Example #1 Il nostro primo script PHP: ciao.php
<html>
<head>
<title>Test PHP</title>
</head>
<body>
<?php echo "Hello World!<p>"; ?>
</body>
</html>
L'output di questo script sarà:
<html> <head> <title>Test PHP</title> </head> <body> Hello World!<p> </body> </html>
Si noti che questo file non è come uno script CGI. Il file non necessita in alcun modo di essere eseguibile o speciale in alcuna maniera. Si pensi ad esso come ad un normale file HTML nel quale sono contenuti uno speciale set di tags che permettono di eseguire una moltitudine di cose interessanti.
Questo programma è molto semplice e sicuramente non era necessario fare ricorso a PHP per creare una pagina come quella. Tutto ciò che essa fa è di visualizzare: Hello World! usando la funzione echo() di PHP.
Se si è provato questo esempio e non ha dato alcun output, o è apparso un pop-up che chiedeva se scaricare la pagina, o se è apparso il file come testo, probabilmente che il server su cui si stanno effettuando le prove non ha abilitato PHP. Provare a chiedere al proprio amministratore di sistema di abilitarlo per voi usando il capitolo del manuale dedicato all'Installazione. Se si vogliono sviluppare in locale script PHP, fare riferimento alla sezione » download. Si può sviluppare senza problemi sul proprio Sistema Operativo in locale, è bene installare anche un web server.
L'obiettivo dell'esempio è quello di mostrare il formato speciale dei tag PHP. In questo esempio abbiamo usato <?php per indicare l'inizio di un tag PHP. Quindi abbiamo scritto la funzione PHP e abbiamo lasciato la modalità PHP usando il tag di chiusura, ?>. All'interno di un file HTML si può entrare ed uscire dalla modalità PHP quante volte si desidera.
Nota: Nota riguardo gli editor di testo Esistomo molti editor di testo e Integrated Development Environment (IDE) che possono essere usati per creare, modificare e gestire file PHP. Una lista parziale di questi strumenti è disponibile qui: » PHP Editor's List. Se si desidera suggerire un nuovo programma, visitare la pagina sopra e chiedere al curatore di aggiungerlo alla lista.
Nota: Nota riguardo i Word Processor Word processor quali StarOffice Writer, Microsoft Word e Abiword non sono una buona scelta per modificare i file PHP.
Se si vogliono provare comunque per scrivere questo script di test, ci si deve assicurare di salvare il file come SOLO TESTO, altrimenti PHP non sarà in grado di leggerlo e quindi non riuscirà ad eseguire lo script.
Nota: Nota riguardo Blocco Note di Windows Se si scrive codice usando l'applicazione di Windows Blocco Note, occorre assicurarsi che i file vengano salvati con estensione .php. (Blocco Note aggiunge automaticamente l'estensione .txt ai file, a meno che non si intraprenda uno dei passi descritti di seguito.)
Quando si salva il file e viene chiesto il nome da assegnargli, scrivere il nome fra virgolette (ad esempio: "ciao.php").
In alternativa, si può cliccare sul menu a tendina 'Documenti di Testo' nella finestra di salvataggio e cambiare l'impostazione in "Tutti i File". A quel punto si può inserire il nome del file, senza usare le virgolette.
Andiamo a fare qualcosa di leggermente più utile. Andremo a controllare che tipo di browser sta utilizzando la persona che visita le nostre pagine. Per fare questo si andrà a controllare la stringa dell'user agent che il browser invia come parte della richiesta HTTP. Quest'informazione viene inviata in una variabile. Le Variabili iniziano sempre con il simbolo di dollaro $ in PHP. La variabile alla quale ci riferiamo adesso è $_SERVER["HTTP_USER_AGENT"].
Nota: Note sulle variabili Autoglobali di PHP $_SERVER è una variabile speciale riservata a PHP la quale contiene tutte le informazioni relative al Web Server. È conosciuta come Variabile autoglobale (o Superglobale). Per maggiori informazioni è possibile vedere la pagina del manuale relativa alle Variabili Autoglobali. Questo tipo di variabili sono state introdotte nella versione » 4.1.0 di PHP. Nelle versioni precedenti abbiamo utilizzato le ormai vecchie $HTTP_SERVER_VARS, oggi in disuso, anche se queste continuano ad esistere. (Potete guardare nelle note del vecchio codice.)
Per visualizzare questa variabile, dobbiamo semplicemente:
Example #1 Stampare video una variable (elemento d'Array)
<?php echo $_SERVER["HTTP_USER_AGENT"]; ?>
L'output (risultato) di questo script potrebbe essere:
Mozilla/4.0 (compatible; MSIE 5.01; Windows NT 5.0)
Ci sono molti types (tipi) di variabili disponibili in PHP. Nell'esempio di sopra abbiamo stampato un elemento di un Array. Gli Array possono essere molto utili.
$_SERVER è soltanto una variabile che automaticamente viene resa diponibile da PHP. È possibile visualizzare una lunga lista nella sezione Variabili riservate del manuale oppure ottenere la lista completa creando un file php nella seguente forma:
Example #2 Mostrare tutte le variabili predefinite di PHP con phpinfo()
<?php phpinfo(); ?>
Se caricate questo documento da un browser riceverete una pagina piena d'informazioni circa PHP, così come la lista di tutte le variabili disponibili.
Potete mettere dichiarazioni multipli di PHP all'interno di un tag di PHP e generare piccoli blocchi di codice che fanno di più di un singolo echo. Per esempio, se desiderassimo controllare per vedere se l'utente usa Internet Explorer potremmo fare qualcosa come questo:
Example #3 Esempi usando le strutture di controllo e le funzioni
<?php
if (strstr($_SERVER["HTTP_USER_AGENT"], "MSIE")) {
echo "Stai usando Internet Explorer<br />";
}
?>
L'output di esempio di questo script potrebbe essere:
Stai usando Internet Explorer<br />
Qui introduciamo una coppia di nuovi concetti. Abbiamo la dichiarazione if (se). Se avete una conoscenza con la sintassi di base usata dal linguaggio C questo dovrebbe sembrare logico per voi. Se non conoscete abbastanza C od un altro linguaggio che utilizza la sintassi qui sopra descritta, dovreste probabilmente prendere qualsiasi libro introduttivo di PHP e leggere i primi capitoli, o leggere la parte del manuale relativa ai Riferimenti del Linguaggio. Potete trovare una lista dei libri di PHP su » http://www.php.net/books.php.
Il secondo concetto che abbiamo introdotto era la chiamata alla funzione strstr(). Questa è una funzione sviluppata in PHP che cerca una stringa all'interno di un'altra stringa. In questo caso abbiamo cercato "MSIE" all'interno della stringa $_SERVER["HTTP_USER_AGENT"]. Se la stringa viene trovata, la funzione restituisce TRUE altrimenti, FALSE. Se restituisce TRUE, la dichiarazione if viene valuta come TRUE ed il codice all'interno dei relativi {braces} (sostegni) sarà eseguito. Altrimenti, non esegue altro. Sentitevi liberi di generare esempi simili, con if, else (altrimenti) ed altre funzioni quali strtoupper() e strlen(). Ogni pagina del manuale, relativa a queste funzioni contiene anche degli esempi pratici.
Possiamo fare un passo avanti e mostrarvi come potete entrare ed uscite dal modo PHP anche dall' interno di un blocco PHP:
Example #4 Intercalare i modi PHP e HTML
<?php
if (strstr($_SERVER["HTTP_USER_AGENT"], "MSIE")) {
?>
<h3>strstr dovrebbe ritornare true</h3>
<center><b>Stai usando Internet Explorer</b></center>
<?php
} else {
?>
<h3>strstr dovrebbe ritornare false</h3>
<center><b>Non stai usando Internet Explorer</b></center>
<?php
}
?>
L'output di esempio di questo script potrebbe essere:
<h3>strstr dovrebbe ritornare true</h3> <center><b>Stai usando Internet Explorer</b></center>
Invece di usare la dichiarazione echo per fare l'output di qualcosa, saltiamo fuori dal modo PHP inviando soltanto HTML puro. Il punto importante da notare qui è che il flusso logico dello script rimane intatto. Solo uno dei blocchi di di HTML finirà per essere inviato come risposta, dipendendo se strstr() ritorna TRUE o FALSE in altre parole, se la stringa MSIE viene trovata o meno.
Una delle caratteritiche più forti di PHP è il modo in cui gestisce i form. Il concetto da comprendere principalmente è che qualsiasi elemento di un form sarà automaticamente disponibile per i vostri script PHP. Per maggiori informazioni ed esempi relativi all'utilizzo dei form consultate la sezione del manuale che si riferisce a le Variabili al di fuori di PHP. A seguire un esempio di un form HTML:
Example #1 Un semplice form HTML
<form action="action.php" method="POST"> Il tuo Nome: <input type="text" name="name" value="" /> La tua età: <input type="text" name="age" value ="" /> <input type="submit"> </form>
Questo form non ha niente di speciale. È un semplice form in HTML che non presenta nessun tipo di tags particolari. Quando l'utente riempie questo form e preme il pulsante submit, viene richiamata la pagina action.php. In questo file il risultato sarà qualcosa di simile:
Example #2 La stampa video di dati dal nostro form
Ciao <?php echo $_POST["name"]; ?>.
La tua età è di <?php echo $_POST["age"]; ?> anni.
Ecco un possibile output di questo script:
Ciao Joe. La tua età è di 22 anni.
Ciò che avviene dovrebbe risultare ovvio. Non c' è altro da aggiungere. Le variabili $_POST["name"] e $_POST["age"] vengono impostate automaticamente dal PHP. Prima avevamo usato la variabile autoglobal $_SERVER, ora invece abbiamo introdotto la variabile autoglobal $_POST che contiene tutti i dati di tipo POST. Notate che il metodo del nostro form è il POST. Se usassimo il metodo GET le informazioni ricavate dal nostro form si troverebbero invece in $_GET. Si può anche usare la variabile $_REQUEST se la provenienza dei dati richiesti non ci interessa. Questa variabile contiene un misto di dati GET, POST, COOKIE e FILE. Vedere anche la funzione import_request_variables().
Da quando il PHP è divenuto un linguaggio di scripting popolare, esistono più fonti che producono listati di codice che si possono adoperare nei propri scripts. La maggioranza degli sviluppatori del PHP ha cercato di renderlo compatibile con le versioni precedenti, perciò uno script creato per una vecchia versione del PHP dovrebbe girare senza modifiche (in teoria) in una più recente, ma in pratica spesso possono servire delle correzioni.
Ecco due delle più importanti modifiche apportate al vecchio codice:
Con quello che sapete ora dovreste essere in grado di comprendere la maggior parte del manuale ed anche i vari scripts di esempio reperibili nelle raccolte di esempi. Inoltre potete trovarne altri sui siti web di php.net nella sezione links: » http://www.php.net/links.php.
Before starting the installation, first you need to know what do you want to use PHP for. There are three main fields you can use PHP, as described in the What can PHP do? section:
For the first and most common form, you need three things: PHP itself, a web server and a web browser. You probably already have a web browser, and depending on your operating system setup, you may also have a web server (e.g. Apache on Linux and MacOS X; IIS on Windows). You may also rent webspace at a company. This way, you don't need to set up anything on your own, only write your PHP scripts, upload it to the server you rent, and see the results in your browser.
In case of setting up the server and PHP on your own, you have two choices for the method of connecting PHP to the server. For many servers PHP has a direct module interface (also called SAPI). These servers include Apache, Microsoft Internet Information Server, Netscape and iPlanet servers. Many other servers have support for ISAPI, the Microsoft module interface (OmniHTTPd for example). If PHP has no module support for your web server, you can always use it as a CGI or FastCGI processor. This means you set up your server to use the CGI executable of PHP to process all PHP file requests on the server.
If you are also interested to use PHP for command line scripting (e.g. write scripts autogenerating some images for you offline, or processing text files depending on some arguments you pass to them), you always need the command line executable. For more information, read the section about writing command line PHP applications. In this case, you need no server and no browser.
With PHP you can also write desktop GUI applications using the PHP-GTK extension. This is a completely different approach than writing web pages, as you do not output any HTML, but manage windows and objects within them. For more information about PHP-GTK, please » visit the site dedicated to this extension. PHP-GTK is not included in the official PHP distribution.
From now on, this section deals with setting up PHP for web servers on Unix and Windows with server module interfaces and CGI executables. You will also find information on the command line executable in the following sections.
PHP source code and binary distributions for Windows can be found at » http://www.php.net/downloads.php. We recommend you to choose a » mirror nearest to you for downloading the distributions.
This section will guide you through the general configuration and installation of PHP on Unix systems. Be sure to investigate any sections specific to your platform or web server before you begin the process.
As our manual outlines in the General Installation Considerations section, we are mainly dealing with web centric setups of PHP in this section, although we will cover setting up PHP for command line usage as well.
There are several ways to install PHP for the Unix platform, either with a compile and configure process, or through various pre-packaged methods. This documentation is mainly focused around the process of compiling and configuring PHP. Many Unix like systems have some sort of package installation system. This can assist in setting up a standard configuration, but if you need to have a different set of features (such as a secure server, or a different database driver), you may need to build PHP and/or your web server. If you are unfamiliar with building and compiling your own software, it is worth checking to see whether somebody has already built a packaged version of PHP with the features you need.
Prerequisite knowledge and software for compiling:
The initial PHP setup and configuration process is controlled by the use of the command line options of the configure script. You could get a list of all available options along with short explanations running ./configure --help. Our manual documents the different options separately. You will find the core options in the appendix, while the different extension specific options are descibed on the reference pages.
When PHP is configured, you are ready to build the module and/or executables. The command make should take care of this. If it fails and you can't figure out why, see the Problems section.
This section contains notes and hints specific to Apache installs of PHP on Unix platforms. We also have instructions and notes for Apache 2 on a separate page.
You can select arguments to add to the configure on line 10 below from the list of core configure options and from extension specific options described at the respective places in the manual. The version numbers have been omitted here, to ensure the instructions are not incorrect. You will need to replace the 'xxx' here with the correct values from your files.
Example #1 Installation Instructions (Apache Shared Module Version) for PHP
1. gunzip apache_xxx.tar.gz 2. tar -xvf apache_xxx.tar 3. gunzip php-xxx.tar.gz 4. tar -xvf php-xxx.tar 5. cd apache_xxx 6. ./configure --prefix=/www --enable-module=so 7. make 8. make install 9. cd ../php-xxx 10. Now, configure your PHP. This is where you customize your PHP with various options, like which extensions will be enabled. Do a ./configure --help for a list of available options. In our example we'll do a simple configure with Apache 1 and MySQL support. Your path to apxs may differ from our example. ./configure --with-mysql --with-apxs=/www/bin/apxs 11. make 12. make install If you decide to change your configure options after installation, you only need to repeat the last three steps. You only need to restart apache for the new module to take effect. A recompile of Apache is not needed. Note that unless told otherwise, 'make install' will also install PEAR, various PHP tools such as phpize, install the PHP CLI, and more. 13. Setup your php.ini file: cp php.ini-dist /usr/local/lib/php.ini You may edit your .ini file to set PHP options. If you prefer your php.ini in another location, use --with-config-file-path=/some/path in step 10. If you instead choose php.ini-recommended, be certain to read the list of changes within, as they affect how PHP behaves. 14. Edit your httpd.conf to load the PHP module. The path on the right hand side of the LoadModule statement must point to the path of the PHP module on your system. The make install from above may have already added this for you, but be sure to check. For PHP 4: LoadModule php4_module libexec/libphp4.so For PHP 5: LoadModule php5_module libexec/libphp5.so 15. And in the AddModule section of httpd.conf, somewhere under the ClearModuleList, add this: For PHP 4: AddModule mod_php4.c For PHP 5: AddModule mod_php5.c 16. Tell Apache to parse certain extensions as PHP. For example, let's have Apache parse the .php extension as PHP. You could have any extension(s) parse as PHP by simply adding more, with each separated by a space. We'll add .phtml to demonstrate. AddType application/x-httpd-php .php .phtml It's also common to setup the .phps extension to show highlighted PHP source, this can be done with: AddType application/x-httpd-php-source .phps 17. Use your normal procedure for starting the Apache server. (You must stop and restart the server, not just cause the server to reload by using a HUP or USR1 signal.)
Alternatively, to install PHP as a static object:
Example #2 Installation Instructions (Static Module Installation for Apache) for PHP
1. gunzip -c apache_1.3.x.tar.gz | tar xf - 2. cd apache_1.3.x 3. ./configure 4. cd .. 5. gunzip -c php-5.x.y.tar.gz | tar xf - 6. cd php-5.x.y 7. ./configure --with-mysql --with-apache=../apache_1.3.x 8. make 9. make install 10. cd ../apache_1.3.x 11. ./configure --prefix=/www --activate-module=src/modules/php5/libphp5.a (The above line is correct! Yes, we know libphp5.a does not exist at this stage. It isn't supposed to. It will be created.) 12. make (you should now have an httpd binary which you can copy to your Apache bin dir if it is your first install then you need to "make install" as well) 13. cd ../php-5.x.y 14. cp php.ini-dist /usr/local/lib/php.ini 15. You can edit /usr/local/lib/php.ini file to set PHP options. Edit your httpd.conf or srm.conf file and add: AddType application/x-httpd-php .php
Nota: Replace php-5 by php-4 and php5 by php4 in PHP 4.
Depending on your Apache install and Unix variant, there are many possible ways to stop and restart the server. Below are some typical lines used in restarting the server, for different apache/unix installations. You should replace /path/to/ with the path to these applications on your systems.
Example #3 Example commands for restarting Apache
1. Several Linux and SysV variants: /etc/rc.d/init.d/httpd restart 2. Using apachectl scripts: /path/to/apachectl stop /path/to/apachectl start 3. httpdctl and httpsdctl (Using OpenSSL), similar to apachectl: /path/to/httpsdctl stop /path/to/httpsdctl start 4. Using mod_ssl, or another SSL server, you may want to manually stop and start: /path/to/apachectl stop /path/to/apachectl startssl
The locations of the apachectl and http(s)dctl binaries often vary. If your system has locate or whereis or which commands, these can assist you in finding your server control programs.
Different examples of compiling PHP for apache are as follows:
./configure --with-apxs --with-pgsql
This will create a libphp5.so (or libphp4.so in PHP 4) shared library that is loaded into Apache using a LoadModule line in Apache's httpd.conf file. The PostgreSQL support is embedded into this library.
./configure --with-apxs --with-pgsql=shared
This will create a libphp4.so shared library for Apache, but it will also create a pgsql.so shared library that is loaded into PHP either by using the extension directive in php.ini file or by loading it explicitly in a script using the dl() function.
./configure --with-apache=/path/to/apache_source --with-pgsql
This will create a libmodphp5.a library, a mod_php5.c and some accompanying files and copy this into the src/modules/php5 directory in the Apache source tree. Then you compile Apache using --activate-module=src/modules/php5/libphp5.a and the Apache build system will create libphp5.a and link it statically into the httpd binary (replace php5 by php4 in PHP 4). The PostgreSQL support is included directly into this httpd binary, so the final result here is a single httpd binary that includes all of Apache and all of PHP.
./configure --with-apache=/path/to/apache_source --with-pgsql=shared
Same as before, except instead of including PostgreSQL support directly into the final httpd you will get a pgsql.so shared library that you can load into PHP from either the php.ini file or directly using dl().
When choosing to build PHP in different ways, you should consider the advantages and drawbacks of each method. Building as a shared object will mean that you can compile apache separately, and don't have to recompile everything as you add to, or change, PHP. Building PHP into apache (static method) means that PHP will load and run faster. For more information, see the Apache » web page on DSO support.
Nota: Apache's default httpd.conf currently ships with a section that looks like this:
Unless you change that to "Group nogroup" or something like that ("Group daemon" is also very common) PHP will not be able to open files.User nobody Group "#-1"
Nota: Make sure you specify the installed version of apxs when using --with-apxs=/path/to/apxs. You must NOT use the apxs version that is in the apache sources but the one that is actually installed on your system.
This section contains notes and hints specific to Apache 2.0 installs of PHP on Unix systems.
L'utilizzo di un threaded MPM non è raccomandato in produzione con Apache2. Usare piuttosto il prefork MPM, oppure utilizzare Apache1. Per informazioni sul motivo, leggere la voce correlata delle FAQ sull'uso di Apache2 con un threaded MPM
You are highly encouraged to take a look at the » Apache Documentation to get a basic understanding of the Apache 2.0 Server.
Nota: PHP and Apache 2.0.x compatibility notes The following versions of PHP are known to work with the most recent version of Apache 2.0.x:
These versions of PHP are compatible to Apache 2.0.40 and later.
- PHP 4.3.0 or later available at » http://www.php.net/downloads.php.
- the latest stable development version. Get the source code » http://snaps.php.net/php5-latest.tar.gz or download binaries for Windows » http://snaps.php.net/win32/php5-win32-latest.zip.
- a prerelease version downloadable from » http://qa.php.net/.
- you have always the option to obtain PHP through » anonymous CVS.
Apache 2.0 SAPI-support started with PHP 4.2.0. PHP 4.2.3 works with Apache 2.0.39, don't use any other version of Apache with PHP 4.2.3. However, the recommended setup is to use PHP 4.3.0 or later with the most recent version of Apache2.
All mentioned versions of PHP will work still with Apache 1.3.x.
Download the most recent version of » Apache 2.0 and a fitting PHP version from the above mentioned places. This quick guide covers only the basics to get started with Apache 2.0 and PHP. For more information read the » Apache Documentation. The version numbers have been omitted here, to ensure the instructions are not incorrect. You will need to replace the 'NN' here with the correct values from your files.
Example #1 Installation Instructions (Apache 2 Shared Module Version)
1. gzip -d httpd-2_0_NN.tar.gz 2. tar xvf httpd-2_0_NN.tar 3. gunzip php-NN.tar.gz 4. tar -xvf php-NN.tar 5. cd httpd-2_0_NN 6. ./configure --enable-so 7. make 8. make install Now you have Apache 2.0.NN available under /usr/local/apache2, configured with loadable module support and the standard MPM prefork. To test the installation use your normal procedure for starting the Apache server, e.g.: /usr/local/apache2/bin/apachectl start and stop the server to go on with the configuration for PHP: /usr/local/apache2/bin/apachectl stop. 9. cd ../php-NN 10. Now, configure your PHP. This is where you customize your PHP with various options, like which extensions will be enabled. Do a ./configure --help for a list of available options. In our example we'll do a simple configure with Apache 2 and MySQL support. Your path to apxs may differ, in fact, the binary may even be named apxs2 on your system. ./configure --with-apxs2=/usr/local/apache2/bin/apxs --with-mysql 11. make 12. make install If you decide to change your configure options after installation, you only need to repeat the last three steps. You only need to restart apache for the new module to take effect. A recompile of Apache is not needed. Note that unless told otherwise, 'make install' will also install PEAR, various PHP tools such as phpize, install the PHP CLI, and more. 13. Setup your php.ini cp php.ini-dist /usr/local/lib/php.ini You may edit your .ini file to set PHP options. If you prefer having php.ini in another location, use --with-config-file-path=/some/path in step 10. If you instead choose php.ini-recommended, be certain to read the list of changes within, as they affect how PHP behaves. 14. Edit your httpd.conf to load the PHP module. The path on the right hand side of the LoadModule statement must point to the path of the PHP module on your system. The make install from above may have already added this for you, but be sure to check. For PHP 4: LoadModule php4_module modules/libphp4.so For PHP 5: LoadModule php5_module modules/libphp5.so 15. Tell Apache to parse certain extensions as PHP. For example, let's have Apache parse the .php extension as PHP. You could have any extension(s) parse as PHP by simply adding more, with each separated by a space. We'll add .phtml to demonstrate. AddType application/x-httpd-php .php .phtml It's also common to setup the .phps extension to show highlighted PHP source, this can be done with: AddType application/x-httpd-php-source .phps 16. Use your normal procedure for starting the Apache server, e.g.: /usr/local/apache2/bin/apachectl start
Following the steps above you will have a running Apache 2.0 with support for PHP as SAPI module. Of course there are many more configuration options available for both, Apache and PHP. For more information use ./configure --help in the corresponding source tree. In case you wish to build a multithreaded version of Apache 2.0 you must overwrite the standard MPM-Module prefork either with worker or perchild. To do so append to your configure line in step 6 above either the option --with-mpm=worker or --with-mpm=perchild. Take care about the consequences and understand what you are doing. For more information read the Apache documentation about the » MPM-Modules.
Nota: If you want to use content negotiation, read the Apache MultiViews FAQ.
Nota: To build a multithreaded version of Apache your system must support threads. This also implies to build PHP with experimental Zend Thread Safety (ZTS). Therefore not all extensions might be available. The recommended setup is to build Apache with the standard prefork MPM-Module.
PHP can be built as a Pike module for the » Caudium webserver. Follow the simple instructions below to install PHP for Caudium.
Example #1 Caudium Installation Instructions
1. Make sure you have Caudium installed prior to attempting to install PHP 4. For PHP 4 to work correctly, you will need Pike 7.0.268 or newer. For the sake of this example we assume that Caudium is installed in /opt/caudium/server/. 2. Change directory to php-x.y.z (where x.y.z is the version number). 3. ./configure --with-caudium=/opt/caudium/server 4. make 5. make install 6. Restart Caudium if it's currently running. 7. Log into the graphical configuration interface and go to the virtual server where you want to add PHP 4 support. 8. Click Add Module and locate and then add the PHP 4 Script Support module. 9. If the documentation says that the 'PHP 4 interpreter isn't available', make sure that you restarted the server. If you did check /opt/caudium/logs/debug/default.1 for any errors related to <filename>PHP4.so</filename>. Also make sure that <filename>caudium/server/lib/[pike-version]/PHP4.so</filename> is present. 10. Configure the PHP Script Support module if needed.
You can of course compile your Caudium module with support for the various extensions available in PHP 4. See the reference pages for extension specific configure options.
Nota: When compiling PHP 4 with MySQL support you must make sure that the normal MySQL client code is used. Otherwise there might be conflicts if your Pike already has MySQL support. You do this by specifying a MySQL install directory the --with-mysql option.
To build PHP as an fhttpd module, answer "yes" to "Build as an fhttpd module?" (the --with-fhttpd=DIR option to configure) and specify the fhttpd source base directory. The default directory is /usr/local/src/fhttpd. If you are running fhttpd, building PHP as a module will give better performance, more control and remote execution capability.
Nota: Support for fhttpd is no longer available as of PHP 4.3.0.
This section contains notes and hints specific to Sun Java System Web Server, Sun ONE Web Server, iPlanet and Netscape server installs of PHP on Sun Solaris.
From PHP 4.3.3 on you can use PHP scripts with the NSAPI module to generate custom directory listings and error pages. Additional functions for Apache compatibility are also available. For support in current web servers read the note about subrequests.
You can find more information about setting up PHP for the Netscape Enterprise Server (NES) here: » http://benoit.noss.free.fr/php/install-php4.html
To build PHP with Sun JSWS/Sun ONE WS/iPlanet/Netscape web servers, enter the proper install directory for the --with-nsapi=[DIR] option. The default directory is usually /opt/netscape/suitespot/. Please also read /php-xxx-version/sapi/nsapi/nsapi-readme.txt.
Install the following packages from » http://www.sunfreeware.com/ or another download site:
export PATH
.
gunzip php-x.x.x.tar.gz
(if you have a .gz dist,
otherwise go to 4).
tar xvf php-x.x.x.tar
cd ../php-x.x.x
For the following step, make sure /opt/netscape/suitespot/ is where your netscape server is installed. Otherwise, change to the correct path and run:
./configure --with-mysql=/usr/local/mysql \ --with-nsapi=/opt/netscape/suitespot/ \ --enable-libgcc
After performing the base install and reading the appropriate readme file, you may need to perform some additional configuration steps.
Firstly you may need to add some paths to the LD_LIBRARY_PATH environment for the server to find all the shared libs. This can best done in the start script for your web server. The start script is often located in: /path/to/server/https-servername/start. You may also need to edit the configuration files that are located in: /path/to/server/https-servername/config/.
Add the following line to mime.types (you can do that by the administration server):
type=magnus-internal/x-httpd-php exts=php
Edit magnus.conf (for servers >= 6) or obj.conf (for servers < 6) and add the following, shlib will vary depending on your system, it will be something like /opt/netscape/suitespot/bin/libphp4.so. You should place the following lines after mime types init.
Init fn="load-modules" funcs="php4_init,php4_execute,php4_auth_trans" shlib="/opt/netscape/suitespot/bin/libphp4.so" Init fn="php4_init" LateInit="yes" errorString="Failed to initialize PHP!" [php_ini="/path/to/php.ini"]
Configure the default object in obj.conf (for virtual server classes [version 6.0+] in their vserver.obj.conf):
<Object name="default"> . . . .#NOTE this next line should happen after all 'ObjectType' and before all 'AddLog' lines Service fn="php4_execute" type="magnus-internal/x-httpd-php" [inikey=value inikey=value ...] . . </Object>
This is only needed if you want to configure a directory that only consists of PHP scripts (same like a cgi-bin directory):
<Object name="x-httpd-php"> ObjectType fn="force-type" type="magnus-internal/x-httpd-php" Service fn=php4_execute [inikey=value inikey=value ...] </Object>
Setup of authentication: PHP authentication cannot be used with any other authentication. ALL AUTHENTICATION IS PASSED TO YOUR PHP SCRIPT. To configure PHP Authentication for the entire server, add the following line to your default object:
<Object name="default"> AuthTrans fn=php4_auth_trans . . . </Object>
To use PHP Authentication on a single directory, add the following:
<Object ppath="d:\path\to\authenticated\dir\*"> AuthTrans fn=php4_auth_trans </Object>
Nota: The stacksize that PHP uses depends on the configuration of the web server. If you get crashes with very large PHP scripts, it is recommended to raise it with the Admin Server (in the section "MAGNUS EDITOR").
Important when writing PHP scripts is the fact that Sun JSWS/Sun ONE WS/iPlanet/Netscape is a multithreaded web server. Because of that all requests are running in the same process space (the space of the web server itself) and this space has only one environment. If you want to get CGI variables like PATH_INFO, HTTP_HOST etc. it is not the correct way to try this in the old PHP way with getenv() or a similar way (register globals to environment, $_ENV). You would only get the environment of the running web server without any valid CGI variables!
Nota: Why are there (invalid) CGI variables in the environment?
Answer: This is because you started the web server process from the admin server which runs the startup script of the web server, you wanted to start, as a CGI script (a CGI script inside of the admin server!). This is why the environment of the started web server has some CGI environment variables in it. You can test this by starting the web server not from the administration server. Use the command line as root user and start it manually - you will see there are no CGI-like environment variables.
Simply change your scripts to get CGI variables in the correct way for PHP 4.x by using the superglobal $_SERVER. If you have older scripts which use $HTTP_HOST, etc., you should turn on register_globals in php.ini and change the variable order too (important: remove "E" from it, because you do not need the environment here):
variables_order = "GPCS" register_globals = On
You can use PHP to generate the error pages for "404 Not Found" or similar. Add the following line to the object in obj.conf for every error page you want to overwrite:
Error fn="php4_execute" code=XXX script="/path/to/script.php" [inikey=value inikey=value...]
Another possibility is to generate self-made directory listings. Just create a PHP script which displays a directory listing and replace the corresponding default Service line for type="magnus-internal/directory" in obj.conf with the following:
Service fn="php4_execute" type="magnus-internal/directory" script="/path/to/script.php" [inikey=value inikey=value...]
The NSAPI module now supports the nsapi_virtual() function (alias: virtual()) to make subrequests on the web server and insert the result in the web page. This function uses some undocumented features from the NSAPI library. On Unix the module automatically looks for the needed functions and uses them if available. If not, nsapi_virtual() is disabled.
Nota: But be warned: Support for nsapi_virtual() is EXPERIMENTAL!!!
The default is to build PHP as a CGI program. This creates a command line interpreter, which can be used for CGI processing, or for non-web-related PHP scripting. If you are running a web server PHP has module support for, you should generally go for that solution for performance reasons. However, the CGI version enables users to run different PHP-enabled pages under different user-ids.
Usando il setup del CGI, il server è aperto a parecchi attacchi. Leggere la sezione sulla sicurezza CGI per capire come difendersi da quest attacchi.
As of PHP 4.3.0, some important additions have happened to PHP. A new SAPI named CLI also exists and it has the same name as the CGI binary. What is installed at {PREFIX}/bin/php depends on your configure line and this is described in detail in the manual section named Using PHP from the command line. For further details please read that section of the manual.
If you have built PHP as a CGI program, you may test your build by typing make test. It is always a good idea to test your build. This way you may catch a problem with PHP on your platform early instead of having to struggle with it later.
Some server supplied environment variables are not defined in the current » CGI/1.1 specification. Only the following variables are defined there: AUTH_TYPE, CONTENT_LENGTH, CONTENT_TYPE, GATEWAY_INTERFACE, PATH_INFO, PATH_TRANSLATED, QUERY_STRING, REMOTE_ADDR, REMOTE_HOST, REMOTE_IDENT, REMOTE_USER, REQUEST_METHOD, SCRIPT_NAME, SERVER_NAME, SERVER_PORT, SERVER_PROTOCOL, and SERVER_SOFTWARE. Everything else should be treated as 'vendor extensions'.
This section contains notes and hints specific to installing PHP on HP-UX systems.
There are two main options for installing PHP on HP-UX systems. Either compile it, or install a pre-compiled binary.
Official pre-compiled packages are located here: » http://software.hp.com/
Until this manual section is rewritten, the documentation about compiling PHP (and related extensions) on HP-UX systems has been removed. For now, consider reading the following external resource: » Building Apache and PHP on HP-UX 11.11
This section contains notes and hints specific to installing PHP on » OpenBSD 3.6.
Using binary packages to install PHP on OpenBSD is the recommended and simplest method. The core package has been separated from the various modules, and each can be installed and removed independently from the others. The files you need can be found on your OpenBSD CD or on the FTP site.
The main package you need to install is php4-core-4.3.8.tgz, which contains the basic engine (plus gettext and iconv). Next, take a look at the module packages, such as php4-mysql-4.3.8.tgz or php4-imap-4.3.8.tgz. You need to use the phpxs command to activate and deactivate these modules in your php.ini.
Example #1 OpenBSD Package Install Example
# pkg_add php4-core-4.3.8.tgz # /usr/local/sbin/phpxs -s # cp /usr/local/share/doc/php4/php.ini-recommended /var/www/conf/php.ini (add in mysql) # pkg_add php4-mysql-4.3.8.tgz # /usr/local/sbin/phpxs -a mysql (add in imap) # pkg_add php4-imap-4.3.8.tgz # /usr/local/sbin/phpxs -a imap (remove mysql as a test) # pkg_delete php4-mysql-4.3.8 # /usr/local/sbin/phpxs -r mysql (install the PEAR libraries) # pkg_add php4-pear-4.3.8.tgz
Read the » packages(7) manual page for more information about binary packages on OpenBSD.
You can also compile up PHP from source using the » ports tree. However, this is only recommended for users familiar with OpenBSD. The PHP 4 port is split into two sub-directories: core and extensions. The extensions directory generates sub-packages for all of the supported PHP modules. If you find you do not want to create some of these modules, use the no_* FLAVOR. For example, to skip building the imap module, set the FLAVOR to no_imap.
Older releases of OpenBSD used the FLAVORS system to compile up a statically linked PHP. Since it is hard to generate binary packages using this method, it is now deprecated. You can still use the old stable ports trees if you wish, but they are unsupported by the OpenBSD team. If you have any comments about this, the current maintainer for the port is Anil Madhavapeddy (avsm at openbsd dot org).
This section contains notes and hints specific to installing PHP on Solaris systems.
Solaris installs often lack C compilers and their related tools. Read this FAQ for information on why using GNU versions for some of these tools is necessary. The required software is as follows:
You can simplify the Solaris install process by using pkgadd to install most of your needed components.
This section contains notes and hints specific to installing PHP on » Debian GNU/Linux.
While you can just download the PHP source and compile it yourself, using Debian's packaging system is the simplest and cleanest method of installing PHP. If you are not familiar with building software on Linux, this is the way to go.
The first decision you need to make is whether you want to install Apache 1.3.x or Apache 2.x. The corresponding PHP packages are respectively named libapache-mod-php* and libapache2-mod-php*. The steps given below will use Apache 1.3.x. Please note that, as of this writing, there is no official Debian packages of PHP 5. Then the steps given below will install PHP 4.
PHP is available in Debian as CGI or CLI flavour too, named respectively php4-cgi and php4-cli. If you need them, you'll just have to reproduce the following steps with the good package names. Another special package you'd want to install is php4-pear. It contains a minimal PEAR installation and the pear commandline utility.
If you need more recent packages of PHP than the Debian's stable ones or if some PHP modules lacks the Debian official repository, perhaps you should take a look at » http://www.apt-get.org/. One of the results found should be » Dotdeb. This unofficial repository is maintained by » Guillaume Plessis and contains Debian packages of the most recent versions of PHP 4 and PHP 5. To use it, just add the to following two lines to your /etc/apt/sources.lists and run apt-get update :
Example #1 The two Dotdeb related lines
deb http://packages.dotdeb.org stable all deb-src http://packages.dotdeb.org stable all
The last thing to consider is whether your list of packages is up to date. If you have not updated it recently, you need to run apt-get update before anything else. This way, you will be using the most recent stable version of the Apache and PHP packages.
Now that everything is in place, you can use the following example to install Apache and PHP:
Example #2 Debian Install Example with Apache 1.3
# apt-get install libapache-mod-php4
APT will automatically install the PHP 4 module for Apache 1.3, and all its dependencies and then activate it. If you're not asked to restart Apache during the install process, you'll have to do it manually :
Example #3 Stopping and starting Apache once PHP 4 is installed
# /etc/init.d/apache stop # /etc/init.d/apache start
In the last section, PHP was installed with only core modules. This may not be what you want and you will soon discover that you need more activated modules, like MySQL, cURL, GD, etc.
When you compile PHP from source yourself, you need to activate modules via the configure command. With APT, you just have to install additional packages. They're all named 'php4-*' (or 'php5-*' if you installed PHP 5 from a third party repository).
Example #4 Getting the list of PHP additional packages
# dpkg -l 'php4-*'
As you can see from the last output, there's a lot of PHP modules that you can install (excluding the php4-cgi, php4-cli or php4-pear special packages). Look at them closely and choose what you need. If you choose a module and you do not have the proper libraries, APT will automatically install all the dependencies for you.
If you choose to add the MySQL, cURL and GD support to PHP the command will look something like this:
Example #5 Install PHP with MySQL, cURL and GD
# apt-get install php4-mysql php4-curl php4-gd
APT will automatically add the appropriate lines to your different php.ini (/etc/php4/apache/php.ini, /etc/php4/cgi/php.ini, etc).
Example #6 These lines activate MySQL, cURL and GD into PHP
extension=mysql.so extension=curl.so extension=gd.so
You'll only have to stop/start Apache as previously to activate the modules.
Example #7 This line activates PHP 4 into Apache
# Include /etc/apache/conf.d/
This section contains notes and hints specific to installing PHP on Mac OS X. There are two slightly different versions of Mac OS X, Client and Server, our manual deals with installing PHP on both systems. Note that PHP is not available for MacOS 9 and earlier versions.
There are a few pre-packaged and pre-compiled versions of PHP for Mac OS X. This can help in setting up a standard configuration, but if you need to have a different set of features (such as a secure server, or a different database driver), you may need to build PHP and/or your web server yourself. If you are unfamiliar with building and compiling your own software, it's worth checking whether somebody has already built a packaged version of PHP with the features you need.
The following resources offer easy to install packages and precompiled binaries for PHP on Mac OS:
PHP has come standard with Macs since OS X version 10.0.0. Enabling PHP with the default web server requires uncommenting a few lines in the Apache configuration file httpd.conf whereas the CGI and/or CLI are enabled by default (easily accessible via the Terminal program).
Enabling PHP using the instructions below is meant for quickly setting up a local development environment. It's highly recommended to always upgrade PHP to the newest version. Like most live software, newer versions are created to fix bugs and add features and PHP being is no different. See the appropriate MAC OS X installation documentation for further details. The following instructions are geared towards a beginner with details provided for getting a default setup to work. All users are encouraged to compile, or install a new packaged version.
The standard installation type is using mod_php, and enabling the bundled mod_php on Mac OS X for the Apache web server (the default web server, that is accessible via System Preferences) involves the following steps:
Nota: One way to open this is by using a Unix based text editor in the Terminal, for example nano, and because the file is owned by root we'll use the sudo command to open it (as root) so for example type the following into the Terminal Application (after, it will prompt for a password): sudo nano /etc/httpd/httpd.conf Noteworthy nano commands: ^w (search), ^o (save), and ^x (exit) where ^ represents the Ctrl key.
With a text editor, uncomment the lines (by removing the #) that look similar to the following (these two lines are often not together, locate them both in the file):
# LoadModule php4_module libexec/httpd/libphp4.so # AddModule mod_php4.c
Be sure the desired extensions will parse as PHP (examples: .php .html and .inc)
Due to the following statement already existing in httpd.conf (as of Mac Panther), once PHP is enabled the .php files will automatically parse as PHP.
<IfModule mod_php4.c> # If php is turned on, we respect .php and .phps files. AddType application/x-httpd-php .php AddType application/x-httpd-php-source .phps # Since most users will want index.php to work we # also automatically enable index.php <IfModule mod_dir.c> DirectoryIndex index.html index.php </IfModule> </IfModule>
The phpinfo() function will display information about PHP. Consider creating a file in the DocumentRoot with the following PHP code:
<?php phpinfo(); ?>
The CLI (or CGI in older versions) is appropriately named php and likely exists as /usr/bin/php. Open up the terminal, read the command line section of the PHP manual, and execute php -v to check the PHP version of this PHP binary. A call to phpinfo() will also reveal this information.
Untar them, and run the configure program on Apache like so.
./configure --exec-prefix=/usr \ --localstatedir=/var \ --mandir=/usr/share/man \ --libexecdir=/System/Library/Apache/Modules \ --iconsdir=/System/Library/Apache/Icons \ --includedir=/System/Library/Frameworks/Apache.framework/Versions/1.3/Headers \ --enable-shared=max \ --enable-module=most \ --target=apache
If you want the compiler to do some optimization, you may also want to add this line:
setenv OPTIM=-O2
Next, go to the PHP 4 source directory and configure it.
./configure --prefix=/usr \
--sysconfdir=/etc \
--localstatedir=/var \
--mandir=/usr/share/man \
--with-xml \
--with-apache=/src/apache_1.3.12
Now, reconfigure Apache to build in PHP 4.
./configure --exec-prefix=/usr \ --localstatedir=/var \ --mandir=/usr/share/man \ --libexecdir=/System/Library/Apache/Modules \ --iconsdir=/System/Library/Apache/Icons \ --includedir=/System/Library/Frameworks/Apache.framework/Versions/1.3/Headers \ --enable-shared=max \ --enable-module=most \ --target=apache \ --activate-module=src/modules/php4/libphp4.a
cp php.ini-dist /usr/local/bin/php.ini
or (if your don't have a local directory)
cp php.ini-dist /usr/bin/php.ini
.
The following instructions will help you install a PHP module for the Apache web server included in MacOS X. This version includes support for the MySQL and PostgreSQL databases. These instructions are graciously provided by » Marc Liyanage.
Be careful when you do this, you could screw up your Apache web server!
Do this to install:
wget http://www.diax.ch/users/liyanage/software/macosx/libphp4.so.gz
,
wait for the download to finish.
gunzip libphp4.so.gz
.
sudo apxs -i -a -n php4 libphp4.so
Now type sudo open -a TextEdit /etc/httpd/httpd.conf
.
TextEdit will open with the web server configuration file. Locate these
two lines towards the end of the file: (Use the Find command)
#AddType application/x-httpd-php .php #AddType application/x-httpd-php-source .phps
sudo apachectl graceful
to restart
the web server.
PHP should now be up and running. You can test it by dropping a file into your Sites folder which is called test.php. Into that file, write this line: <?php phpinfo() ?>.
Now open up 127.0.0.1/~your_username/test.php in your web browser. You should see a status table with information about the PHP module.
This section applies to Windows 98/Me and Windows NT/2000/XP/2003. PHP will not work on 16 bit platforms such as Windows 3.1 and sometimes we refer to the supported Windows platforms as Win32. Windows 95 is no longer supported as of PHP 4.3.0.
There are two main ways to install PHP for Windows: either manually or by using the installer.
If you have Microsoft Visual Studio, you can also build PHP from the original source code.
Once you have PHP installed on your Windows system, you may also want to load various extensions for added functionality.
There are several all-in-one installers over the Internet, but none of those are endorsed by PHP.net, as we believe that using one of the official windows packages from » http://www.php.net/downloads.php is the best choice to have your system secure and optimised.
The Windows PHP installer for later versions of PHP is built using MSI technology using the Wix Toolkit (» http://wix.sourceforge.net/). It will install and configure PHP and all the built-in and PECL extensions, as well as configure many of the popular web servers such as IIS, Apache, and Xitami.
First, install your selected HTTP (web) server on your system, and make sure that it works. Then proceed with one of the following install types.
Run the MSI installer and follow the instructions provided by the installation wizard. You will be prompted to select the Web Server you wish to configure first, along with any configuration details needed.
You will then be prompted to select which features and extensions you wish to install and enable. By selecting "Will be installed on local hard drive" in the drop-down menu for each item you can trigger whether to install the feature or not. By selecting "Entire feature will be installed on local hard drive", you will be able to install all sub-features of the included feature ( for example by selecting this options for the feature "PDO" you will install all PDO Drivers ).
It is not recommended to install all extensions by default, since many other them require dependencies from outside PHP in order to function properly. Instead, use the Installation Repair Mode that can be triggered thru the 'Add/Remove Programs' control panel to enable or disable extensions and features after installation.
The installer then sets up PHP to be used in Windows and the php.ini file, and configures certain web servers to use PHP. The installer will currently configure IIS, Apache, Xitami, and Sambar Server; if you are using a different web server you'll need to configure it manually.
The installer also supports a silent mode, which is helpful for Systems Administrators to deploy PHP easily. To use silent mode:
msiexec.exe /i php-VERSION-win32-install.msi /q
You can control the install directory by passing it as a parameter to the install. For example, to install to e:\php:
msiexec.exe /i php-VERSION-win32-install.msi /q INSTALLDIR=e:\php
You can also specify what features to install. For example, to install the mysqli extension and the CGI executable:
msiexec.exe /i php-VERSION-win32-install.msi /q ADDLOCAL=cgi,ext_php_mysqli
The current list of Features to install is as follows:
MainExecutable - php.exe executable ScriptExecutable - php-win.exe executable ext_php_* - the various extensions ( for example: ext_php_mysql for MySQL ) apache13 - Apache 1.3 module apache20 - Apache 2.0 module apache22 - Apache 2,2 module apacheCGI - Apache CGI executable iis4ISAPI - IIS ISAPI module iis4CGI - IIS CGI executable NSAPI - Sun/iPlanet/Netscape server module Xitami - Xitami CGI executable Sambar - Sambar Server ISAPI module CGI - php-cgi.exe executable PEAR - PEAR installer Manual - PHP Manual in CHM Format
For more information on installing MSI installers from the command line, visit » http://msdn.microsoft.com/library/en-us/msi/setup/command_line_options.asp
To upgrade, run the installer either graphically or from the command line as normal. The installer will read your current install options, remove your old installation, and reinstall PHP with the same options as before. It is recommended that you use this method of keeping PHP updated instead of manually replacing the files in the installation directory.
The Windows PHP installer is available from the downloads page at » http://www.php.net/downloads.php. This installs the CGI version of PHP and for IIS, PWS, and Xitami, it configures the web server as well. The installer does not include any extra external PHP extensions (php_*.dll) as you'll only find those in the Windows Zip Package and PECL downloads.
Nota: While the Windows installer is an easy way to make PHP work, it is restricted in many aspects as, for example, the automatic setup of extensions is not supported. Use of the installer isn't the preferred method for installing PHP.
First, install your selected HTTP (web) server on your system, and make sure that it works.
Run the executable installer and follow the instructions provided by the installation wizard. Two types of installation are supported - standard, which provides sensible defaults for all the settings it can, and advanced, which asks questions as it goes along.
The installation wizard gathers enough information to set up the php.ini file, and configure certain web servers to use PHP. One of the web servers the PHP installer does not configure for is Apache, so you'll need to configure it manually.
Once the installation has completed, the installer will inform you if you need to restart your system, restart the server, or just start using PHP.
Be aware, that this setup of PHP is not secure. If you would like to have a secure PHP setup, you'd better go on the manual way, and set every option carefully. This automatically working setup gives you an instantly working PHP installation, but it is not meant to be used on online servers.
This install guide will help you manually install and configure PHP with a web server on Microsoft Windows. To get started you'll need to download the zip binary distribution from the downloads page at » http://www.php.net/downloads.php.
Although there are many all-in-one installation kits, and we also distribute a PHP installer for Microsoft Windows, we recommend you take the time to setup PHP yourself as this will provide you with a better understanding of the system, and enables you to install PHP extensions easily when needed.
Nota: Upgrading from a previous PHP version Previous editions of the manual suggest moving various ini and DLL files into your SYSTEM (i.e. C:\WINDOWS) folder and while this simplifies the installation procedure it makes upgrading difficult. We advise you remove all of these files (like php.ini and PHP related DLLs from the Windows SYSTEM folder) before moving on with a new PHP installation. Be sure to backup these files as you might break the entire system. The old php.ini might be useful in setting up the new PHP as well. And as you'll soon learn, the preferred method for installing PHP is to keep all PHP related files in one directory and have this directory available to your systems PATH.
Nota: MDAC requirements If you use Microsoft Windows 98/NT4 download the latest version of the Microsoft Data Access Components (MDAC) for your platform. MDAC is available at » http://msdn.microsoft.com/data/. This requirement exists because ODBC is built into the distributed Windows binaries.
The following steps should be completed on all installations before any server specific instructions are performed:
Extract the distribution file into a directory of your choice. If you are installing PHP 4, extract to C:\, as the zip file expands to a foldername like php-4.3.7-Win32. If you are installing PHP 5, extract to C:\php as the zip file doesn't expand as in PHP 4. You may choose a different location but do not have spaces in the path (like C:\Program Files\PHP) as some web servers will crash if you do.
The directory structure extracted from the zip is different for PHP versions 4 and 5 and look like as follows:
Example #1 PHP 4 package structure
c:\php | +--cli | | | |-php.exe -- CLI executable - ONLY for command line scripting | +--dlls -- support DLLs required by some extensions | | | |-expat.dll | | | |-fdftk.dll | | | |-... | +--extensions -- extension DLLs for PHP | | | |-php_bz2.dll | | | |-php_cpdf.dll | | | |-.. | +--mibs -- support files for SNMP | +--openssl -- support files for Openssl | +--pdf-related -- support files for PDF | +--sapi -- SAPI (server module support) DLLs | | | |-php4apache.dll | | | |-php4apache2.dll | | | |-.. | +--PEAR -- initial copy of PEAR | | |-go-pear.bat -- PEAR setup script | |-.. | |-php.exe -- CGI executable | |-.. | |-php.ini-dist -- default php.ini settings | |-php.ini-recommended -- recommended php.ini settings | |-php4ts.dll -- core PHP DLL | |-...
Or:
Example #2 PHP 5 package structure
c:\php | +--dev | | | |-php5ts.lib | +--ext -- extension DLLs for PHP | | | |-php_bz2.dll | | | |-php_cpdf.dll | | | |-.. | +--extras | | | +--mibs -- support files for SNMP | | | +--openssl -- support files for Openssl | | | +--pdf-related -- support files for PDF | | | |-mime.magic | +--pear -- initial copy of PEAR | | |-go-pear.bat -- PEAR setup script | |-fdftk.dll | |-.. | |-php-cgi.exe -- CGI executable | |-php-win.exe -- executes scripts without an opened command prompt | |-php.exe -- CLI executable - ONLY for command line scripting | |-.. | |-php.ini-dist -- default php.ini settings | |-php.ini-recommended -- recommended php.ini settings | |-php5activescript.dll | |-php5apache.dll | |-php5apache2.dll | |-.. | |-php5ts.dll -- core PHP DLL | |-...
Notice the differences and similarities. Both PHP 4 and PHP 5 have a CGI executable, a CLI executable, and server modules, but they are located in different folders and/or have different names. While PHP 4 packages have the server modules in the sapi folder, PHP 5 distributions have no such directory and instead they're in the PHP folder root. The supporting DLLs for the PHP 5 extensions are also not in a seperate directory.
Nota: In PHP 4, you should move all files located in the dll and sapi folders to the main folder (e.g. C:\php).
Here is a list of server modules shipped with PHP 4 and PHP 5:
sapi/php4activescript.dll (php5activescript.dll) - ActiveScript engine, allowing you to embed PHP in your Windows applications.
sapi/php4apache.dll (php5apache.dll) - Apache 1.3.x module.
sapi/php4apache2.dll (php5apache2.dll) - Apache 2.0.x module.
sapi/php5apache2_2.dll - Apache 2.2.x module.
sapi/php4isapi.dll (php5isapi.dll) - ISAPI Module for ISAPI compliant web servers like IIS 4.0/PWS 4.0 or newer.
sapi/php4nsapi.dll (php5nsapi.dll) - Sun/iPlanet/Netscape server module.
sapi/php4pi3web.dll (no equivalent in PHP 5) - Pi3Web server module.
Server modules provide significantly better performance and additional functionality compared to the CGI binary. The CLI version is designed to let you use PHP for command line scripting. More information about CLI is available in the chapter about using PHP from the command line.
The SAPI modules have been significantly improved as of the 4.1 release, however, in older systems you may encounter server errors or other server modules failing, such as ASP.
The CGI and CLI binaries, and the web server modules all require the php4ts.dll (php5ts.dll) file to be available to them. You have to make sure that this file can be found by your PHP installation. The search order for this DLL is as follows:
The same directory from where php.exe is called, or in case you use a SAPI module, the web server's directory (e.g. C:\Program Files\Apache Group\Apache2\bin).
Any directory in your Windows PATH environment variable.
To make php4ts.dll / php5ts.dll available you have three options: copy the file to the Windows system directory, copy the file to the web server's directory, or add your PHP directory, C:\php to the PATH. For better maintenance, we advise you to follow the last option, add C:\php to the PATH, because it will be simpler to upgrade PHP in the future. Read more about how to add your PHP directory to PATH in the corresponding FAQ entry (and then don't forget to restart the computer - logoff isn't enough).
The next step is to set up a valid configuration file for PHP, php.ini. There are two ini files distributed in the zip file, php.ini-dist and php.ini-recommended. We advise you to use php.ini-recommended, because we optimized the default settings in this file for performance, and security. Read this well documented file carefully because it has changes from php.ini-dist that will drastically affect your setup. Some examples are display_errors being off and magic_quotes_gpc being off. In addition to reading these, study the ini settings and set every element manually yourself. If you would like to achieve the best security, then this is the way for you, although PHP works fine with these default ini files. Copy your chosen ini-file to a directory that PHP is able to find and rename it to php.ini. PHP searches for php.ini in the locations described in Runtime Configuration section.
If you are running Apache 2, the simpler option is to use the PHPIniDir directive (read the installation on Apache 2 page), otherwise your best option is to set the PHPRC environment variable. This process is explained in the following FAQ entry.
Nota: If you're using NTFS on Windows NT, 2000, XP or 2003, make sure that the user running the web server has read permissions to your php.ini (e.g. make it readable by Everyone).
The following steps are optional:
Edit your new php.ini file. If you plan to use OmniHTTPd, do not follow the next step. Set the doc_root to point to your web servers document_root. For example:
doc_root = c:\inetpub\wwwroot // for IIS/PWS doc_root = c:\apache\htdocs // for Apache
PHP is now setup on your system. The next step is to choose a web server, and enable it to run PHP. Choose a web server from the table of contents.
This section contains notes specific to the ActiveScript installation.
ActiveScript is a Windows only SAPI that enables you to use PHP script in any ActiveScript compliant host, like Windows Script Host, ASP/ASP.NET, Windows Script Components or Microsoft Scriptlet control.
As of PHP 5.0.1, ActiveScript has been moved to the » PECL repository. La DLL per questa estensione PECL può essere scaricata dalla pagina » PHP Downloads oppure da » http://pecl4win.php.net/
Nota: You should read the manual installation steps first!
After installing PHP, you should download the ActiveScript DLL (php5activescript.dll) and place it in the main PHP folder (e.g. C:\php).
After having all the files needed, you must register the DLL on your system. To achieve this, open a Command Prompt window (located in the Start Menu). Then go to your PHP directory by typing something like cd C:\php. To register the DLL just type regsvr32 php5activescript.dll.
To test if ActiveScript is working, create a new file, named test.wsf (the extension is very important) and type:
<job id="test">
<script language="PHPScript">
$WScript->Echo("Hello World!");
</script>
</job>
Nota: In PHP 4, the engine was named 'ActivePHP', so if you are using PHP 4, you should replace 'PHPScript' with 'ActivePHP' in the above example.
Nota: ActiveScript doesn't use the default php.ini file. Instead, it will look only in the same directory as the .exe that caused it to load. You should create php-activescript.ini and place it in that folder, if you wish to load extensions, etc.
This section contains notes and hints specific to IIS (Microsoft Internet Information Server).
Usando il setup del CGI, il server è aperto a parecchi attacchi. Leggere la sezione sulla sicurezza CGI per capire come difendersi da quest attacchi.
PHP may be installed as a CGI binary, or with the ISAPI module. In either case, you need to start the Microsoft Management Console (may appear as 'Internet Services Manager', either in your Windows NT 4.0 Option Pack branch or the Control Panel=>Administrative Tools under Windows 2000/XP). Then right click on your Web server node (this will most probably appear as 'Default Web Server'), and select 'Properties'.
If you want to use the CGI binary, do the following:
To use the ISAPI module, do the following:
With IIS 6 (2003 Server), open up the IIS Manager, go to Web Service Extensions, choose "Add a new Web service extension", enter in a name such as PHP, choose the Add button and for the value browse to either the ISAPI file (php4isapi.dll or php5isapi.dll) or CGI (php.exe or php-cgi.exe) then check "Set extension status to Allowed" and click OK.
In order to use index.php as a default content page, do the following: From within the Documents tab, choose Add. Type in index.php and click OK. Adjust the order by choosing Move Up or Move Down. This is similar to setting DirectoryIndex with Apache.
The steps above must be repeated for each extension that is to be associated with PHP scripts. .php is the most common although .php3 may be required for legacy applications.
If you experience 100% CPU usage after some time, turn off the IIS setting Cache ISAPI Application.
PWS 4 does not support ISAPI, only PHP CGI should be used.
The recommended method for configuring these servers is to use the REG file included with the distribution (pws-php4cgi.reg in the SAPI folder for PHP 4, or pws-php5cgi.reg in the main folder for PHP 5). You may want to edit this file and make sure the extensions and PHP install directories match your configuration. Or you can follow the steps below to do it manually.
These steps involve working directly with the Windows registry. One error here can leave your system in an unstable state. We highly recommend that you back up your registry first. The PHP Development team will not be held responsible if you damage your registry.
The following steps do not affect the web server installation and only apply if you want your PHP scripts to be executed when they are run from the command line (ex. run C:\myscripts\test.php) or by double clicking on them in a directory viewer window. You may wish to skip these steps as you might prefer the PHP files to load into a text editor when you double click on them.
PWS and IIS 3 users now have a fully operational system. IIS 3 users can use a nifty » tool from Steven Genusa to configure their script maps.
This section contains notes and hints specific to Apache 1.3.x installs of PHP on Microsoft Windows systems. There are also instructions and notes for Apache 2 on a separate page.
Nota: Please read the manual installation steps first!
There are two ways to set up PHP to work with Apache 1.3.x on Windows. One is to use the CGI binary (php.exe for PHP 4 and php-cgi.exe for PHP 5), the other is to use the Apache Module DLL. In either case you need to edit your httpd.conf to configure Apache to work with PHP, and then restart the server.
It is worth noting here that now the SAPI module has been made more stable under Windows, we recommend it's use above the CGI binary, since it is more transparent and secure.
Although there can be a few variations of configuring PHP under Apache, these are simple enough to be used by the newcomer. Please consult the Apache Documentation for further configuration directives.
After changing the configuration file, remember to restart the server, for example, NET STOP APACHE followed by NET START APACHE, if you run Apache as a Windows Service, or use your regular shortcuts.
Nota: Ricordare che quando si aggiungono valori di path nei file di configurazione Apache su Windows, tutti i backslash some c:\directory\file.ext devono essere convertiti in slash, come c:/directory/file.ext. Uno slash finale può essere necessario per le cartelle.
You should add the following lines to your Apache httpd.conf file:
Example #1 PHP as an Apache 1.3.x module
This assumes PHP is installed to c:\php. Adjust the path if this is not the case.
For PHP 4:
# Add to the end of the LoadModule section # Don't forget to copy this file from the sapi directory! LoadModule php4_module "C:/php/php4apache.dll" # Add to the end of the AddModule section AddModule mod_php4.c
For PHP 5:
# Add to the end of the LoadModule section LoadModule php5_module "C:/php/php5apache.dll" # Add to the end of the AddModule section AddModule mod_php5.c
For both:
# Add this line inside the <IfModule mod_mime.c> conditional brace AddType application/x-httpd-php .php # For syntax highlighted .phps files, also add AddType application/x-httpd-php-source .phps
If you unzipped the PHP package to C:\php\ as described in the Manual Installation Steps section, you need to insert these lines to your Apache configuration file to set up the CGI binary:
Example #2 PHP and Apache 1.3.x as CGI
ScriptAlias /php/ "c:/php/" AddType application/x-httpd-php .php # For PHP 4 Action application/x-httpd-php "/php/php.exe" # For PHP 5 Action application/x-httpd-php "/php/php-cgi.exe" # specify the directory where php.ini is SetEnv PHPRC C:/php
Usando il setup del CGI, il server è aperto a parecchi attacchi. Leggere la sezione sulla sicurezza CGI per capire come difendersi da quest attacchi.
If you would like to present PHP source files syntax highlighted, there is no such convenient option as with the module version of PHP. If you chose to configure Apache to use PHP as a CGI binary, you will need to use the highlight_file() function. To do this simply create a PHP script file and add this code: <?php highlight_file('some_php_script.php'); ?>.
This section contains notes and hints specific to Apache 2.0.x installs of PHP on Microsoft Windows systems. We also have instructions and notes for Apache 1.3.x users on a separate page.
Nota: You should read the manual installation steps first!
Nota: Apache 2.2.x Support Users of Apache 2.2.x may use the documentation below except the appropriate DLL file is named php5apache2_2.dll and it only exists as of PHP 5.2.0. See also » http://snaps.php.net/
L'utilizzo di un threaded MPM non è raccomandato in produzione con Apache2. Usare piuttosto il prefork MPM, oppure utilizzare Apache1. Per informazioni sul motivo, leggere la voce correlata delle FAQ sull'uso di Apache2 con un threaded MPM
You are highly encouraged to take a look at the » Apache Documentation to get a basic understanding of the Apache 2.0.x Server. Also consider to read the » Windows specific notes for Apache 2.0.x before reading on here.
Nota: PHP and Apache 2.0.x compatibility notes The following versions of PHP are known to work with the most recent version of Apache 2.0.x:
These versions of PHP are compatible to Apache 2.0.40 and later.
- PHP 4.3.0 or later available at » http://www.php.net/downloads.php.
- the latest stable development version. Get the source code » http://snaps.php.net/php5-latest.tar.gz or download binaries for Windows » http://snaps.php.net/win32/php5-win32-latest.zip.
- a prerelease version downloadable from » http://qa.php.net/.
- you have always the option to obtain PHP through » anonymous CVS.
Apache 2.0 SAPI-support started with PHP 4.2.0. PHP 4.2.3 works with Apache 2.0.39, don't use any other version of Apache with PHP 4.2.3. However, the recommended setup is to use PHP 4.3.0 or later with the most recent version of Apache2.
All mentioned versions of PHP will work still with Apache 1.3.x.
Apache 2.0.x is designed to run on Windows NT 4.0, Windows 2000 or Windows XP. At this time, support for Windows 9x is incomplete. Apache 2.0.x is not expected to work on those platforms at this time.
Download the most recent version of » Apache 2.0.x and a fitting PHP version. Follow the Manual Installation Steps and come back to go on with the integration of PHP and Apache.
There are two ways to set up PHP to work with Apache 2.0.x on Windows. One is to use the CGI binary the other is to use the Apache module DLL. In either case you need to edit your httpd.conf to configure Apache to work with PHP and then restart the server.
Nota: Ricordare che quando si aggiungono valori di path nei file di configurazione Apache su Windows, tutti i backslash some c:\directory\file.ext devono essere convertiti in slash, come c:/directory/file.ext. Uno slash finale può essere necessario per le cartelle.
You need to insert these three lines to your Apache httpd.conf configuration file to set up the CGI binary:
Example #1 PHP and Apache 2.0 as CGI
ScriptAlias /php/ "c:/php/" AddType application/x-httpd-php .php # For PHP 4 Action application/x-httpd-php "/php/php.exe" # For PHP 5 Action application/x-httpd-php "/php/php-cgi.exe"
Usando il setup del CGI, il server è aperto a parecchi attacchi. Leggere la sezione sulla sicurezza CGI per capire come difendersi da quest attacchi.
You need to insert these two lines to your Apache httpd.conf configuration file to set up the PHP module for Apache 2.0:
Example #2 PHP and Apache 2.0 as Module
# For PHP 4 do something like this: LoadModule php4_module "c:/php/php4apache2.dll" # Don't forget to copy the php4apache2.dll file from the sapi directory! AddType application/x-httpd-php .php # For PHP 5 do something like this: LoadModule php5_module "c:/php/php5apache2.dll" AddType application/x-httpd-php .php # configure the path to php.ini PHPIniDir "C:/php"
Nota: Remember to substitute your actual path to PHP for the c:/php/ in the above examples. Take care to use either php4apache2.dll or php5apache2.dll in your LoadModule directive and not php4apache.dll or php5apache.dll as the latter ones are designed to run with Apache 1.3.x.
Nota: If you want to use content negotiation, read related FAQ.
Don't mix up your installation with DLL files from different PHP versions. You have the only choice to use the DLL's and extensions that ship with your downloaded PHP version.
This section contains notes and hints specific to Sun Java System Web Server, Sun ONE Web Server, iPlanet and Netscape server installs of PHP on Windows.
From PHP 4.3.3 on you can use PHP scripts with the NSAPI module to generate custom directory listings and error pages. Additional functions for Apache compatibility are also available. For support in current web servers read the note about subrequests.
To install PHP as a CGI handler, do the following:
Make a file association from the command line. Type the following two lines:
assoc .php=PHPScript ftype PHPScript=c:\php\php.exe %1 %*
More details about setting up PHP as a CGI executable can be found here: » http://benoit.noss.free.fr/php/install-php.html
To install PHP with NSAPI, do the following:
Make a file association from the command line. Type the following two lines:
assoc .php=PHPScript ftype PHPScript=c:\php\php.exe %1 %*
Edit magnus.conf (for servers >= 6) or obj.conf (for servers < 6) and add the following: You should place the lines after mime types init.
Init fn="load-modules" funcs="php4_init,php4_execute,php4_auth_trans" shlib="c:/php/sapi/php4nsapi.dll" Init fn="php4_init" LateInit="yes" errorString="Failed to initialise PHP!" [php_ini="c:/path/to/php.ini"]
Configure the default object in obj.conf (for virtual server classes [Sun Web Server 6.0+] in their vserver.obj.conf): In the <Object name="default"> section, place this line necessarily after all 'ObjectType' and before all 'AddLog' lines:
Service fn="php4_execute" type="magnus-internal/x-httpd-php" [inikey=value inikey=value ...]
This is only needed if you want to configure a directory that only consists of PHP scripts (same like a cgi-bin directory):
<Object name="x-httpd-php"> ObjectType fn="force-type" type="magnus-internal/x-httpd-php" Service fn=php4_execute [inikey=value inikey=value ...] </Object>
Nota: More details about setting up PHP as an NSAPI filter can be found here: » http://benoit.noss.free.fr/php/install-php4.html
Nota: The stacksize that PHP uses depends on the configuration of the web server. If you get crashes with very large PHP scripts, it is recommended to raise it with the Admin Server (in the section "MAGNUS EDITOR").
Important when writing PHP scripts is the fact that Sun JSWS/Sun ONE WS/iPlanet/Netscape is a multithreaded web server. Because of that all requests are running in the same process space (the space of the web server itself) and this space has only one environment. If you want to get CGI variables like PATH_INFO, HTTP_HOST etc. it is not the correct way to try this in the old PHP way with getenv() or a similar way (register globals to environment, $_ENV). You would only get the environment of the running web server without any valid CGI variables!
Nota: Why are there (invalid) CGI variables in the environment?
Answer: This is because you started the web server process from the admin server which runs the startup script of the web server, you wanted to start, as a CGI script (a CGI script inside of the admin server!). This is why the environment of the started web server has some CGI environment variables in it. You can test this by starting the web server not from the administration server. Use the command line as root user and start it manually - you will see there are no CGI-like environment variables.
Simply change your scripts to get CGI variables in the correct way for PHP 4.x by using the superglobal $_SERVER. If you have older scripts which use $HTTP_HOST, etc., you should turn on register_globals in php.ini and change the variable order too (important: remove "E" from it, because you do not need the environment here):
variables_order = "GPCS" register_globals = On
You can use PHP to generate the error pages for "404 Not Found" or similar. Add the following line to the object in obj.conf for every error page you want to overwrite:
Error fn="php4_execute" code=XXX script="/path/to/script.php" [inikey=value inikey=value...]
Another possibility is to generate self-made directory listings. Just create a PHP script which displays a directory listing and replace the corresponding default Service line for type="magnus-internal/directory" in obj.conf with the following:
Service fn="php4_execute" type="magnus-internal/directory" script="/path/to/script.php" [inikey=value inikey=value...]
The NSAPI module now supports the nsapi_virtual() function (alias: virtual()) to make subrequests on the web server and insert the result in the web page. The problem is, that this function uses some undocumented features from the NSAPI library.
Under Unix this is not a problem, because the module automatically looks for the needed functions and uses them if available. If not, nsapi_virtual() is disabled.
Under Windows limitations in the DLL handling need the use of a automatic detection of the most recent ns-httpdXX.dll file. This is tested for servers till version 6.1. If a newer version of the Sun server is used, the detection fails and nsapi_virtual() is disabled.
If this is the case, try the following: Add the following parameter to php4_init in magnus.conf/obj.conf:
Init fn=php4_init ... server_lib="ns-httpdXX.dll"
You can check the status by using the phpinfo() function.
Nota: But be warned: Support for nsapi_virtual() is EXPERIMENTAL!!!
This section contains notes and hints specific to » OmniHTTPd on Windows.
Nota: You should read the manual installation steps first!
Usando il setup del CGI, il server è aperto a parecchi attacchi. Leggere la sezione sulla sicurezza CGI per capire come difendersi da quest attacchi.
You need to complete the following steps to make PHP work with OmniHTTPd. This is a CGI executable setup. SAPI is supported by OmniHTTPd, but some tests have shown that it is not so stable to use PHP as an ISAPI module.
Nota: Important for CGI users Read the faq on cgi.force_redirect for important details. This directive needs to be set to 0.
Install OmniHTTPd server.
Right click on the blue OmniHTTPd icon in the system tray and select Properties
Click on Web Server Global Settings
On the 'External' tab, enter: virtual = .php | actual = c:\php\php.exe (use php-cgi.exe if installing PHP 5), and use the Add button.
On the Mime tab, enter: virtual = wwwserver/stdcgi | actual = .php, and use the Add button.
Click OK
Repeat steps 2 - 6 for each extension you want to associate with PHP.
Nota: Some OmniHTTPd packages come with built in PHP support. You can choose at setup time to do a custom setup, and uncheck the PHP component. We recommend you to use the latest PHP binaries. Some OmniHTTPd servers come with PHP 4 beta distributions, so you should choose not to set up the built in support, but install your own. If the server is already on your machine, use the Replace button in Step 4 and 5 to set the new, correct information.
This section contains notes and hints specific to the » Sambar Server for Windows.
Nota: You should read the manual installation steps first!
This list describes how to set up the ISAPI module to work with the Sambar server on Windows.
Find the file called mappings.ini (in the config directory) in the Sambar install directory.
Open mappings.ini and add the following line under [ISAPI]:
Example #1 ISAPI configuration of Sambar
#for PHP 4 *.php = c:\php\php4isapi.dll #for PHP 5 *.php = c:\php\php5isapi.dll
Now restart the Sambar server for the changes to take effect.
Nota: If you intend to use PHP to communicate with resources which are held on a different computer on your network, then you will need to alter the account used by the Sambar Server Service. The default account used for the Sambar Server Service is LocalSystem which will not have access to remote resources. The account can be amended by using the Services option from within the Windows Control Panel Administation Tools.
This section contains notes and hints specific to » Xitami on Windows.
Nota: You should read the manual installation steps first!
This list describes how to set up the PHP CGI binary to work with Xitami on Windows.
Nota: Important for CGI users Read the faq on cgi.force_redirect for important details. This directive needs to be set to 0. If you want to use $_SERVER['PHP_SELF'] you have to enable the cgi.fix_pathinfo directive.
Usando il setup del CGI, il server è aperto a parecchi attacchi. Leggere la sezione sulla sicurezza CGI per capire come difendersi da quest attacchi.
Make sure the web server is running, and point your browser to xitamis admin console (usually http://127.0.0.1/admin), and click on Configuration.
Navigate to the Filters, and put the extension which PHP should parse (i.e. .php) into the field File extensions (.xxx).
In Filter command or script put the path and name of your PHP CGI executable i.e. C:\php\php.exe for PHP 4, or C:\php\php-cgi.exe for PHP 5.
Press the 'Save' icon.
Restart the server to reflect changes.
This chapter teaches how to compile PHP from sources on windows, using Microsoft's tools. To compile PHP with cygwin, please refer to Installation on Unix systems.
This step-by-step quick-start guide was written in March of 2008, running Windows XP Service Pack 2 with all the latest updates and building PHP 5.2.5 and PHP 5.3. Experiences using different tools may differ.
Download and install:
+-C:\work | +-bindlib_w32 | | +-Debug | | | +-resolv.lib | | | +-... | | +-... | +-win32build | | +-bin | | +-include | | +-lib | +-php-5.2.5 | | +-build | | +-win32 | | +-...
C:\Program Files\Microsoft Visual Studio 9.0\VC> set "PATH=C:\work\win32build\bin;%PATH%" C:\Program Files\Microsoft Visual Studio 9.0\VC>
To compile and build PHP you need a Microsoft Development Environment. The following environments are supported:
While VC6 (Microsoft Visual C++ 6.0) is used to perform official Windows builds, it can no longer be downloaded from Microsoft's website. New users seeking to build PHP for free must use Microsoft Visual C++ 2005 Express Edition and its auxiliary components.
Nota: Combined, these components are very large and will require over one gigabyte of disk space.
Setting up Microsoft Visual C++ 2005 Express is rather involved, and requires the installation of three separate packages and various compatibility changes. Be sure to keep track of the paths in which these programs are installed into. Download and install the following programs:
There are a few post-installation steps:
Finally, when using MSVC 2005 Express from the command line, several environment variables must be set up. vsvars32.bat usually found in C:\Program Files\Microsoft Visual Studio 8\Common7\Tools (search for the file if otherwise) contains these declarations. The PATH, INCLUDE and LIB environment variables need the corresponding bin, include and lib directories of the two newly installed SDKs added to them.
Nota: The .NET SDK paths may already be present in the vsvars32.bat file, as this SDK installs itself into the same directory as Microsoft Visual C++ 2005 Express.
To extract the downloaded files you will also need a ZIP extraction utility. Windows XP and newer already include this functionality built-in.
Before you get started, you have to download:
Finally, you are going to need the source to PHP itself. You can get the latest development version using » anonymous CVS, a » snapshot or the most recent released » source tarball.
After downloading the required packages you have to extract them in a proper place:
+--C:\work | | | +--bindlib_w32 | | | | | +--arpa | | | | | +--conf | | | | | +--... | | | +--php-5.x.x | | | | | +--build | | | | | +--... | | | | | +--win32 | | | | | +--... | | | +--win32build | | | | | +--bin | | | | | +--include | | | | | +--lib
If you aren't using » Cygwin, you must also create the directories C:\usr\local\lib and then copy bison.simple from C:\work\win32build\bin to C:\usr\local\lib.
Nota: If you want to use PEAR and the comfortable command line installer, the CLI-SAPI is mandatory. For more information about PEAR and the installer read the documentation at the » PEAR website.
You must build the resolv.lib library. Decide whether you want to have debug symbols available (bindlib - Win32 Debug) or not (bindlib - Win32 Release), but please remember the choice you made, because the debug build will only link with PHP when it is also built in debug mode. Build the appropriate configuration:
This chapter explains how to compile PHP >=5 using the new build system, which is CLI-based and very similar with the main PHP's Unix build system.
Nota: This build system isn't available in PHP 4. Please refer to Building from source instead.
Before starting, be sure you have read Building from source and you have built all needed libraries, like » Libxml or » ICU (needed for PHP >= 6).
First you should open a Visual Studio Command Prompt, which should be available under the Start menu. A regular Command Prompt window shouldn't work, as probably it doesn't have the necessary environment variables set. Then type something like cd C:\work\php-5.x.x to enter in the PHP source dir. Now you are ready to start configuring PHP.
The second step is running the buildconf batch file to make the configure script, by scanning the folder for config.w32 files. By default this command will also search in the following directories: pecl; ..\pecl; pecl\rpc; ..\pecl\rpc. Since PHP 5.1.0, you can change this behaviour by using the --add-modules-dir argument (e.g. cscript /nologo win32/build/buildconf.js --add-modules-dir=../php-gtk2 --add-modules-dir=../pecl).
The third step is configuring. To view the list of the available configuration options type cscript /nologo configure.js --help. After choosing the options that you will enable/disable, type something like: cscript /nologo configure.js --disable-foo --enable-fun-ext. Using --enable-foo=shared will attempt to build the 'foo' extension as a shared, dynamically loadable module.
The last step is compiling. To achieve this just issue the command nmake. The generated files (e.g. .exe and .dll) will be placed in either Release_TS or Debug_TS directories (if built with Thread safety), or in the Release or Debug directories otherwise.
Optionally you may also run PHP's test suite, by typing nmake test. If you want to run just a specific test, you may use the 'TESTS' variable (e.g. nmake /D TESTS=ext/sqlite/tests test - will only run sqlite's tests). To delete the files that were created during the compilation, you can use the nmake clean command.
A very useful configure option to build snapshots is --enable-snapshot-build, which add a new compiling mode (nmake build-snap). This tries to build every extension available (as shared, by default), but it will ignore build errors in individual extensions or SAPI.
Compiling PHP using the DSW files isn't supported as of PHP 5, as a much more flexible system was made available. Anyway, you can still use them, but keep in mind that they are not maintained very often, so you can have compiling problems. To compile PHP 4 for windows, this is the only available way though.
The first step is to configure MVC++ to prepare for compiling. Launch Microsoft Visual C++, and from the menu select Tools => Options. In the dialog, select the directories tab. Sequentially change the dropdown to Executables, Includes, and Library files. Your entries should look like this:
The best way to get started is to build the CGI version:
It is possible to do minor customization to the build process by editing the main/config.win32.h file. For example you can change the default location of php.ini, the built-in extensions, and the default location for your extensions.
Next you may want to build the CLI version which is designed to use PHP from the command line. The steps are the same as for building the CGI version, except you have to select the php4ts_cli - Win32 Debug_TS or php4ts_cli - Win32 Release_TS project file. After a successful compiling run you will find the php.exe in either the directory Release_TS\cli\ or Debug_TS\cli\.
In order to build the SAPI module (php4isapi.dll) for integrating PHP with Microsoft IIS, set your active configuration to php4isapi-whatever-config and build the desired dll.
After installing PHP and a web server on Windows, you will probably want to install some extensions for added functionality. You can choose which extensions you would like to load when PHP starts by modifying your php.ini. You can also load a module dynamically in your script using dl().
The DLLs for PHP extensions are prefixed with php_.
Many extensions are built into the Windows version of PHP. This means additional DLL files, and the extension directive, are not used to load these extensions. The Windows PHP Extensions table lists extensions that require, or used to require, additional PHP DLL files. Here's a list of built in extensions:
In PHP 4 (updated PHP 4.3.11): BCMath, Caledar, COM, Ctype, FTP, MySQL, ODBC, Overload, PCRE, Session, Tokenizer, WDDX, XML e Zlib
In PHP 5 (updated PHP 5.0.4), the following changes exist. Built in: DOM, LibXML, Iconv, SimpleXML, SPL e SQLite. And the following are no longer built in: MySQL and Overload.
The default location PHP searches for extensions is C:\php4\extensions in PHP 4 and C:\php5 in PHP 5. To change this setting to reflect your setup of PHP edit your php.ini file:
You will need to change the extension_dir setting to point to the directory where your extensions lives, or where you have placed your php_*.dll files. For example:
extension_dir = C:\php\extensions
Enable the extension(s) in php.ini you want to use by uncommenting the extension=php_*.dll lines in php.ini. This is done by deleting the leading ; from the extension you want to load.
Example #1 Enable Bzip2 extension for PHP-Windows
// change the following line from ... ;extension=php_bz2.dll // ... to extension=php_bz2.dll
Some of the extensions need extra DLLs to work. Couple of them can be found in the distribution package, in the C:\php\dlls\ folder in PHP 4 or in the main folder in PHP 5, but some, for example Oracle (php_oci8.dll) require DLLs which are not bundled with the distribution package. If you are installing PHP 4, copy the bundled DLLs from C:\php\dlls folder to the main C:\php folder. Don't forget to include C:\php in the system PATH (this process is explained in a separate FAQ entry).
Some of these DLLs are not bundled with the PHP distribution. See each extensions documentation page for details. Also, read the manual section titled Installation of PECL extensions for details on PECL. An increasingly large number of PHP extensions are found in PECL, and these extensions require a separate download.
Nota: If you are running a server module version of PHP remember to restart your web server to reflect your changes to php.ini.
The following table describes some of the extensions available and required additional dlls.
| Extension | Description | Notes |
|---|---|---|
| php_bz2.dll | bzip2 compression functions | None |
| php_calendar.dll | Calendar conversion functions | Built in since PHP 4.0.3 |
| php_crack.dll | Crack functions | None |
| php_ctype.dll | ctype family functions | Built in since PHP 4.3.0 |
| php_curl.dll | CURL, Client URL library functions | Requires: libeay32.dll, ssleay32.dll (bundled) |
| php_dba.dll | DBA: DataBase (dbm-style) Abstraction layer functions | None |
| php_dbase.dll | dBase functions | None |
| php_dbx.dll | dbx functions | |
| php_domxml.dll | DOM XML functions | PHP <= 4.2.0 requires: libxml2.dll (bundled) PHP >= 4.3.0 requires: iconv.dll (bundled) |
| php_dotnet.dll | .NET functions | PHP <= 4.1.1 |
| php_exif.dll | EXIF functions | php_mbstring.dll. And, php_exif.dll must be loaded after php_mbstring.dll in php.ini. |
| php_fbsql.dll | FrontBase functions | PHP <= 4.2.0 |
| php_fdf.dll | FDF: Forms Data Format functions. | Requires: fdftk.dll (bundled) |
| php_filepro.dll | filePro functions | Read-only access |
| php_ftp.dll | FTP functions | Built-in since PHP 4.0.3 |
| php_gd.dll | GD library image functions | Removed in PHP 4.3.2. Also note that truecolor functions are not available in GD1, instead, use php_gd2.dll. |
| php_gd2.dll | GD library image functions | GD2 |
| php_gettext.dll | Gettext functions | PHP <= 4.2.0 requires gnu_gettext.dll (bundled), PHP >= 4.2.3 requires libintl-1.dll, iconv.dll (bundled). |
| php_hyperwave.dll | HyperWave functions | None |
| php_iconv.dll | ICONV characterset conversion | Requires: iconv-1.3.dll (bundled), PHP >=4.2.1 iconv.dll |
| php_ifx.dll | Informix functions | Requires: Informix libraries |
| php_iisfunc.dll | IIS management functions | None |
| php_imap.dll | IMAP POP3 and NNTP functions | None |
| php_ingres.dll | Ingres II functions | Requires: Ingres II libraries |
| php_interbase.dll | InterBase functions | Requires: gds32.dll (bundled) |
| php_java.dll | Java functions | PHP <= 4.0.6 requires: jvm.dll (bundled) |
| php_ldap.dll | LDAP functions | PHP <= 4.2.0 requires libsasl.dll (bundled), PHP >= 4.3.0 requires libeay32.dll, ssleay32.dll (bundled) |
| php_mbstring.dll | Multi-Byte String functions | None |
| php_mcrypt.dll | Mcrypt Encryption functions | Requires: libmcrypt.dll |
| php_mhash.dll | Mhash functions | PHP >= 4.3.0 requires: libmhash.dll (bundled) |
| php_mime_magic.dll | Mimetype functions | Requires: magic.mime (bundled) |
| php_ming.dll | Ming functions for Flash | None |
| php_msql.dll | mSQL functions | Requires: msql.dll (bundled) |
| php_mssql.dll | MSSQL functions | Requires: ntwdblib.dll (bundled) |
| php_mysql.dll | MySQL functions | PHP >= 5.0.0, requires libmysql.dll (bundled) |
| php_mysqli.dll | MySQLi functions | PHP >= 5.0.0, requires libmysql.dll (libmysqli.dll in PHP <= 5.0.2) (bundled) |
| php_oci8.dll | Oracle 8 functions | Requires: Oracle 8.1+ client libraries |
| php_openssl.dll | OpenSSL functions | Requires: libeay32.dll (bundled) |
| php_overload.dll | Object overloading functions | Built in since PHP 4.3.0 |
| php_pdf.dll | PDF functions | None |
| php_pgsql.dll | PostgreSQL functions | None |
| php_printer.dll | Printer functions | None |
| php_shmop.dll | Shared Memory functions | None |
| php_snmp.dll | SNMP get and walk functions | NT only! |
| php_soap.dll | SOAP functions | PHP >= 5.0.0 |
| php_sockets.dll | Socket functions | None |
| php_sybase_ct.dll | Sybase functions | Requires: Sybase client libraries |
| php_tidy.dll | Tidy functions | PHP >= 5.0.0 |
| php_tokenizer.dll | Tokenizer functions | Built in since PHP 4.3.0 |
| php_w32api.dll | W32api functions | None |
| php_xmlrpc.dll | XML-RPC functions | PHP >= 4.2.1 requires: iconv.dll (bundled) |
| php_xslt.dll | XSLT functions | PHP <= 4.2.0 requires sablot.dll, expat.dll (bundled). PHP >= 4.2.1 requires sablot.dll, expat.dll, iconv.dll (bundled). |
| php_yaz.dll | YAZ functions | Requires: yaz.dll (bundled) |
| php_zip.dll | Zip File functions | Read only access |
| php_zlib.dll | ZLib compression functions | Built in since PHP 4.3.0 |
» PECL is a repository of PHP extensions that are made available to you via the » PEAR packaging system. This section of the manual is intended to demonstrate how to obtain and install PECL extensions.
These instructions assume /your/phpsrcdir/ is the path to the PHP source distribution, and that extname is the name of the PECL extension. Adjust accordingly. These instructions also assume a familiarity with the » pear command. The information in the PEAR manual for the pear command also applies to the pecl command.
To be useful, a shared extension must be built, installed, and loaded. The methods described below provide you with various instructions on how to build and install the extensions, but they do not automatically load them. Extensions can be loaded by adding an extension directive. To this php.ini file, or through the use of the dl() function.
When building PHP modules, it's important to have known-good versions of the required tools (autoconf, automake, libtool, etc.) See the » Anonymous CVS Instructions for details on the required tools, and required versions.
There are several options for downloading PECL extensions, such as:
$ cvs -d:pserver:cvsread@cvs.php.net:/repository login
$ cvs -d:pserver:cvsread@cvs.php.net:/repository co pecl/extname
As with any other PHP extension DLL, installation is as simple as copying the PECL extension DLLs into the extension_dir folder and loading them from php.ini. For example, add the following line to your php.ini:
extension=php_extname.dll
After doing this, restart the web service.
PECL makes it easy to create shared PHP extensions. Using the » pecl command, do the following:
$ pecl install extname
This will download the source for extname, compile, and install extname.so into your extension_dir. extname.so may then be loaded via php.ini
By default, the pecl command will not install packages that are marked with the alpha or beta state. If no stable packages are available, you may install a beta package using the following command:
$ pecl install extname-beta
You may also install a specific version using this variant:
$ pecl install extname-0.1
Nota: After enabling the extension in php.ini, restarting the web service is required for the changes to be picked up.
Sometimes, using the pecl installer is not an option. This could be because you're behind a firewall, or it could be because the extension you want to install is not available as a PECL compatible package, such as unreleased extensions from CVS. If you need to build such an extension, you can use the lower-level build tools to perform the build manually.
The phpize command is used to prepare the build environment for a PHP extension. In the following sample, the sources for an extension are in a directory named extname:
$ cd extname $ phpize $ ./configure $ make # make install
A successful install will have created extname.so and put it into the PHP extensions directory. You'll need to and adjust php.ini and add an extension=extname.so line before you can use the extension.
If the system is missing the phpize command, and precompiled packages (like RPM's) are used, be sure to also install the appropriate devel version of the PHP package as they often include the phpize command along with the appropriate header files to build PHP and its extensions.
Execute phpize --help to display additional usage information.
You might find that you need to build a PECL extension statically into your PHP binary. To do this, you'll need to place the extension source under the php-src/ext/ directory and tell the PHP build system to regenerate its configure script.
$ cd /your/phpsrcdir/ext $ pecl download extname $ gzip -d < extname.tgz | tar -xvf - $ mv extname-x.x.x extname
This will result in the following directory:
/your/phpsrcdir/ext/extname
From here, force PHP to rebuild the configure script, and then build PHP as normal:
$ cd /your/phpsrcdir $ rm configure $ ./buildconf --force $ ./configure --help $ ./configure --with-extname --enable-someotherext --with-foobar $ make $ make install
Nota: To run the 'buildconf' script you need autoconf 2.13 and automake 1.4+ (newer versions of autoconf may work, but are not supported).
Whether --enable-extname or --with-extname is used depends on the extension. Typically an extension that does not require external libraries uses --enable. To be sure, run the following after buildconf:
$ ./configure --help | grep extname
Some problems are more common than others. The most common ones are listed in the PHP FAQ, part of this manual.
If you are still stuck, someone on the PHP installation mailing list may be able to help you. You should check out the archive first, in case someone already answered someone else who had the same problem as you. The archives are available from the support page on » http://www.php.net/support.php. To subscribe to the PHP installation mailing list, send an empty mail to » php-install-subscribe@lists.php.net. The mailing list address is » php-install@lists.php.net.
If you want to get help on the mailing list, please try to be precise and give the necessary details about your environment (which operating system, what PHP version, what web server, if you are running PHP as CGI or a server module, modalità sicura, etc...), and preferably enough code to make others able to reproduce and test your problem.
If you think you have found a bug in PHP, please report it. The PHP developers probably don't know about it, and unless you report it, chances are it won't be fixed. You can report bugs using the bug-tracking system at » http://bugs.php.net/. Please do not send bug reports in mailing list or personal letters. The bug system is also suitable to submit feature requests.
Read the » How to report a bug document before submitting any bug reports!
The configuration file (php.ini) is read when PHP starts up. For the server module versions of PHP, this happens only once when the web server is started. For the CGI and CLI version, it happens on every invocation.
php.ini is searched in these locations (in order):
SAPI module specific location (PHPIniDir directive in Apache 2, -c command line option in CGI and CLI, php_ini parameter in NSAPI, PHP_INI_PATH environment variable in THTTPD)
The PHPRC environment variable. Before PHP 5.2.0 this was checked after the registry key mentioned below.
As of PHP 5.2.0, the following registry locations are searched in order: HKEY_LOCAL_MACHINE\SOFTWARE\PHP\x.y.z\IniFilePath, HKEY_LOCAL_MACHINE\SOFTWARE\PHP\x.y\IniFilePath and HKEY_LOCAL_MACHINE\SOFTWARE\PHP\x\IniFilePath, where x, y and z mean the PHP major, minor and release versions.
HKEY_LOCAL_MACHINE\SOFTWARE\PHP\IniFilePath (Windows Registry location)
Current working directory (except CLI)
The web server's directory (for SAPI modules), or directory of PHP (otherwise in Windows)
Windows directory (C:\windows or C:\winnt) (for Windows), or --with-config-file-path compile time option
If php-SAPI.ini exists (where SAPI is used SAPI, so the filename is e.g. php-cli.ini or php-apache.ini), it's used instead of php.ini. SAPI name can be determined by php_sapi_name().
Nota: The Apache web server changes the directory to root at startup causing PHP to attempt to read php.ini from the root filesystem if it exists.
The php.ini directives handled by extensions are documented respectively on the pages of the extensions themselves. The list of the core directives is available in the appendix. Probably not all PHP directives are documented in the manual though. For a complete list of directives available in your PHP version, please read your well commented php.ini file. Alternatively, you may find the » the latest php.ini from CVS helpful too.
Example #1 php.ini example
; any text on a line after an unquoted semicolon (;) is ignored [php] ; section markers (text within square brackets) are also ignored ; Boolean values can be set to either: ; true, on, yes ; or false, off, no, none register_globals = off track_errors = yes ; you can enclose strings in double-quotes include_path = ".:/usr/local/lib/php" ; backslashes are treated the same as any other character include_path = ".;c:\php\lib"
Since PHP 5.1.0, it is possible to refer to existing .ini variables from within .ini files. Example: open_basedir = ${open_basedir} ":/new/dir".
When using PHP as an Apache module, you can also change the configuration settings using directives in Apache configuration files (e.g. httpd.conf) and .htaccess files. You will need "AllowOverride Options" or "AllowOverride All" privileges to do so.
There are several Apache directives that allow you to change the PHP configuration from within the Apache configuration files. For a listing of which directives are PHP_INI_ALL, PHP_INI_PERDIR, or PHP_INI_SYSTEM, have a look at the List of php.ini directives appendix.
php_value
name
value
Sets the value of the specified directive. Can be used only with PHP_INI_ALL and PHP_INI_PERDIR type directives. To clear a previously set value use none as the value.
Nota: Don't use
php_valueto set boolean values.php_flag(see below) should be used instead.
php_flag
name
on|off
Used to set a boolean configuration directive. Can be used only with PHP_INI_ALL and PHP_INI_PERDIR type directives.
php_admin_value
name
value
Sets the value of the specified directive.
This can not be used in .htaccess files.
Any directive type set with php_admin_value
can not be overridden by .htaccess.
To clear a previously set value use none as the value.
php_admin_flag
name
on|off
Used to set a boolean configuration directive.
This can not be used in .htaccess files.
Any directive type set with php_admin_flag
can not be overridden by .htaccess.
Example #1 Apache configuration example
<IfModule mod_php5.c> php_value include_path ".:/usr/local/lib/php" php_admin_flag safe_mode on </IfModule> <IfModule mod_php4.c> php_value include_path ".:/usr/local/lib/php" php_admin_flag safe_mode on </IfModule>
PHP constants do not exist outside of PHP. For example, in httpd.conf you can not use PHP constants such as E_ALL or E_NOTICE to set the error_reporting directive as they will have no meaning and will evaluate to 0. Use the associated bitmask values instead. These constants can be used in php.ini
When running PHP on Windows, the configuration values can be modified on a per-directory basis using the Windows registry. The configuration values are stored in the registry key HKLM\SOFTWARE\PHP\Per Directory Values, in the sub-keys corresponding to the path names. For example, configuration values for the directory c:\inetpub\wwwroot would be stored in the key HKLM\SOFTWARE\PHP\Per Directory Values\c\inetpub\wwwroot. The settings for the directory would be active for any script running from this directory or any subdirectory of it. The values under the key should have the name of the PHP configuration directive and the string value. PHP constants in the values are not parsed. However, only configuration values changeable in PHP_INI_USER can be set this way, PHP_INI_PERDIR values can not.
Regardless of how you run PHP, you can change certain values at runtime of your scripts through ini_set(). See the documentation on the ini_set() page for more information.
If you are interested in a complete list of configuration settings on your system with their current values, you can execute the phpinfo() function, and review the resulting page. You can also access the values of individual configuration directives at runtime using ini_get() or get_cfg_var().
Quando il PHP inizia a esaminare un file, cerca i tag di apertura e di chiusura, che indicano dove iniziare e terminare l'interpretazione del codice. Questa tecnica permette al PHP di essere incorporato in tutte le tipologie di documenti, poichè ogni cosa esterna ai tag di apertura e di chiusura viene ignoarat dal parser PHP. Il più delle volte si vedrà codice PHP racchiuso in documenti HTML, come nel seguente esempio.
<p>This is going to be ignored.</p>
<?php echo 'While this is going to be parsed.'; ?>
<p>This will also be ignored.</p>
Si possono usare anche strutture più avanzate:
Example #1 Escape avanzato
<?php
if ($expression) {
?>
<strong>This is true.</strong>
<?php
} else {
?>
<strong>This is false.</strong>
<?php
}
?>
Esistono 4 set di tag che possono essere utilizzati per delimitare blocchi di codice PHP. Soltanto due di questi (<?php. . .?> e <script language="php">. . .</script>) sono sempre disponibili. Gli altri due sono i tag brevi e i tag stile ASP e possono essere attivati o disattivati tramite il file di configurazione php.ini. Sebbene i tag brevi o quelli in stile ASP possano essere pratici, questi sono meno portabili e, in generale, sconsigliati.
Nota: Occorre notare che se si intende inserire codice PHP all'interno di testi XMl o XHTML, occorre utilizzare <?php ?> per essere conformi allo standard XML.
Example #2 Tag di apertura e di chiusura
1. <?php echo 'se si vogliono produrre documenti XHTML o XML, si utilizzi questo modo'; ?>
2. <script language="php">
echo 'alcuni editor (tipo FrontPage) non
amano le istruzioni di elaborazione';
</script>
3. <? echo 'questo è il più semplice, ovvero come istruzione SGML'; ?>
<?= espressione ?> Questa è un'abbreviazione per "<? echo espressione ?>"
4. <% echo 'Opzionalmente puoi utilizzare tag nello stile ASP'; %>
<%= $variable; # Questo è una abbreviazione per "<% echo ..." %>
Sebbene i tag utilizzati negli esempi 1 e 2 siano sempre disponibili, l'esempio uno rappresenta la situazione più comunemente utilizzata, e la più raccomandata dei due.
I tag brevi (esempio tre) sono disponibili soltanto se sono stati abilitati tramite il parametro short_open_tag del php.ini, oppure se il PHP è stato configurato con --enable-short-tags.
Nota: Se si utilizza il PHP 3 si può anche avere disponibili i tag brevi tramite la funzione short_tags(). Questo vale solo per il PHP 3!
I tag in stile ASP (esempio quattro) sono disponibili soltanto quando sono abilitati tramite il parametro asp_tags del php.ini
Nota: Il supporto per i tag nello stile ASP è stato aggiunto nella versione 3.0.4.
Nota: L'utilizzo dei tag brevi dovrebbe essere evitato nello sviluppo di applicazioni o librerie destinate alla distribuzione o destinati a server di produzione PHP di cui non si ha il controllo poichè questi tag potrebbero non essere attivi sul server di destinazione. Per avere maggiore portabilità, codice redistribuibile, occorre essere certi di non utilizzare i tag brevi.
Come in C od in Perl, il PHP richiede che le istruzioni siano chiuse dal punto e virgola al termine di ogni istruzione. I tag di chiusura di un blocco di codice PHP implicano in automatico il punto e virgola; non occorre, pertanto, inserire il punto e virgola per chiudere l'ultima riga di un blocco PHP. Il tag di chiusura del blocco include il newline immediatamente seguente, se presente.
<?php
echo 'Questo è un test';
?>
<?php echo 'Questo è un test' ?>
Nota: Il tag di chiusura di un blocco PHP alla fine di un file è opzionale, ed in alcuni casi è utile non utilizzarlo soprattutto quando si utilizza l'output buffering e le funzioni include() o require().
Il PHP supporta i commenti dei linguaggi 'C', 'C++' e stile shell (stile Perl) di Unix. Per esempio:
<?php
echo 'Questo è un test'; // Questo è un commento su una linea nella stile c++
/* Questo è un commento su più linee
ancora un'altra linea di commento */
echo 'Questo è un altro test';
echo 'Un ultimo test'; # Questo è un commento stile shell Unix
?>
Lo stile di commento su "una linea", attualmente commenta solo fino alla fine della linea o del blocco corrente di codice PHP. Questo significa che l'eventuale codice HTML posto dopo // ?> sarà stampato: ?> esce dalla modalità PHP e ritorna in modalità HTML, e quindi // non può influenzare quest'ultima. Se l'impostazione asp_tags è abilitata, il PHP si comporta allo stesso modo con // %>. Tuttavia il tag </script> non esce dalla modalità PHP nei commenti di una linea.
<h1>Questo è un <?# echo 'semplice';?> esempio.</h1>
<p>L'intestazione qui sopra dirà 'Questo è un esempio'.</p>
I commenti in stile C terminano alla prima occorrenza di */. Occorre fare attenzione nel non annidare i commenti di stile C, situazione che si presenta quando si commentano larghi blocchi di codice.
<?php
/*
echo 'Questo è un test'; /* Questo commento causerà dei problemi */
*/
?>
PHP supports eight primitive types.
Four scalar types:
Two compound types:
And finally two special types:
This manual also introduces some pseudo-types for readability reasons:
And the pseudo-variable $... .
Some references to the type "double" may remain in the manual. Consider double the same as float; the two names exist only for historic reasons.
The type of a variable is not usually set by the programmer; rather, it is decided at runtime by PHP depending on the context in which that variable is used.
Nota: To check the type and value of an expression, use the var_dump() function. To get a human-readable representation of a type for debugging, use the gettype() function. To check for a certain type, do not use gettype(), but rather the is_type functions. Some examples:
<?php
$a_bool = TRUE; // a boolean
$a_str = "foo"; // a string
$a_str2 = 'foo'; // a string
$an_int = 12; // an integer
echo gettype($a_bool); // prints out: boolean
echo gettype($a_str); // prints out: string
// If this is an integer, increment it by four
if (is_int($an_int)) {
$an_int += 4;
}
// If $bool is a string, print it out
// (does not print out anything)
if (is_string($a_bool)) {
echo "String: $a_bool";
}
?>
To forcibly convert a variable to a certain type, either cast the variable or use the settype() function on it.
Note that a variable may be evaluated with different values in certain situations, depending on what type it is at the time. For more information, see the section on Type Juggling. The type comparison tables may also be useful, as they show examples of various type-related comparisons.
This is the simplest type. A boolean expresses a truth value. It can be either TRUE or FALSE.
Nota: The boolean type was introduced in PHP 4.
To specify a boolean literal, use the keywords TRUE or FALSE. Both are case-insensitive.
<?php
$foo = True; // assign the value TRUE to $foo
?>
Typically, some kind of operator which returns a boolean value, and the value is passed on to a control structure.
<?php
// == is an operator which test
// equality and returns a boolean
if ($action == "show_version") {
echo "The version is 1.23";
}
// this is not necessary...
if ($show_separators == TRUE) {
echo "<hr>\n";
}
// ...because instead, this can be used:
if ($show_separators) {
echo "<hr>\n";
}
?>
To explicitly convert a value to boolean, use the (bool) or (boolean) casts. However, in most cases the cast is unncecessary, since a value will be automatically converted if an operator, function or control structure requires a boolean argument.
See also Type Juggling.
When converting to boolean, the following values are considered FALSE:
Every other value is considered TRUE (including any resource).
-1 is considered TRUE, like any other non-zero (whether negative or positive) number!
<?php
var_dump((bool) ""); // bool(false)
var_dump((bool) 1); // bool(true)
var_dump((bool) -2); // bool(true)
var_dump((bool) "foo"); // bool(true)
var_dump((bool) 2.3e5); // bool(true)
var_dump((bool) array(12)); // bool(true)
var_dump((bool) array()); // bool(false)
var_dump((bool) "false"); // bool(true)
?>
An integer is a number of the set Z = {..., -2, -1, 0, 1, 2, ...}.
See also:
Integers can be specified in decimal (base 10), hexadecimal (base 16), or octal (base 8) notation, optionally preceded by a sign (- or +).
To use octal notation, precede the number with a 0 (zero). To use hexadecimal notation precede the number with 0x.
Example #1 Integer literals
<?php
$a = 1234; // decimal number
$a = -123; // a negative number
$a = 0123; // octal number (equivalent to 83 decimal)
$a = 0x1A; // hexadecimal number (equivalent to 26 decimal)
?>
Formally, the structure for integer literals is:
decimal : [1-9][0-9]*
| 0
hexadecimal : 0[xX][0-9a-fA-F]+
octal : 0[0-7]+
integer : [+-]?decimal
| [+-]?hexadecimal
| [+-]?octal
The size of an integer is platform-dependent, although a maximum value of about two billion is the usual value (that's 32 bits signed). PHP does not support unsigned integers. Integer size can be determined using the constant PHP_INT_SIZE, and maximum value using the constant PHP_INT_MAX since PHP 4.4.0 and PHP 5.0.5.
If an invalid digit is given in an octal integer (i.e. 8 or 9), the rest of the number is ignored.
Example #2 Octal weirdness
<?php
var_dump(01090); // 010 octal = 8 decimal
?>
If PHP encounters a number beyond the bounds of the integer type, it will be interpreted as a float instead. Also, an operation which results in a number beyond the bounds of the integer type will return a float instead.
<?php
$large_number = 2147483647;
var_dump($large_number);
// output: int(2147483647)
$large_number = 2147483648;
var_dump($large_number);
// output: float(2147483648)
// it's true also for hexadecimal specified integers between 2^31 and 2^32-1:
var_dump( 0xffffffff );
// output: float(4294967295)
// this doesn't go for hexadecimal specified integers above 2^32-1:
var_dump( 0x100000000 );
// output: int(2147483647)
$million = 1000000;
$large_number = 50000 * $million;
var_dump($large_number);
// output: float(50000000000)
?>
Unfortunately, there was a bug in PHP which caused this to not always work correctly when negative numbers were involved. For example, the result of -50000 * $million is -429496728. However, when both operands were positive, there was no problem.
This was fixed in PHP 4.1.0.
There is no integer division operator in PHP. 1/2 yields the float 0.5. The value can be casted to an integer to round it downwards, or the round() function provides finer control over rounding.
<?php
var_dump(25/7); // float(3.5714285714286)
var_dump((int) (25/7)); // int(3)
var_dump(round(25/7)); // float(4)
?>
To explicitly convert a value to integer, use either the (int) or (integer) casts. However, in most cases the cast is not needed, since a value will be automatically converted if an operator, function or control structure requires an integer argument. A value can also be converted to integer with the intval() function.
See also: type-juggling.
FALSE will yield 0 (zero), and TRUE will yield 1 (one).
When converting from float to integer, the number will be rounded towards zero.
If the float is beyond the boundaries of integer (usually +/- 2.15e+9 = 2^31), the result is undefined, since the float doesn't have enough precision to give an exact integer result. No warning, not even a notice will be issued when this happens!
Never cast an unknown fraction to integer, as this can sometimes lead to unexpected results.
<?php
echo (int) ( (0.1+0.7) * 10 ); // echoes 7!
?>
See also the warning about float precision.
The behaviour of converting to integer is undefined for other types. Do not rely on any observed behaviour, as it can change without notice.
Floating point numbers (also known as "floats", "doubles", or "real numbers") can be specified using any of the following syntaxes:
<?php
$a = 1.234;
$b = 1.2e3;
$c = 7E-10;
?>
Formally:
LNUM [0-9]+
DNUM ([0-9]*[\.]{LNUM}) | ({LNUM}[\.][0-9]*)
EXPONENT_DNUM (({LNUM} | {DNUM}) [eE][+-]? {LNUM})
The size of a float is platform-dependent, although a maximum of ~1.8e308 with a precision of roughly 14 decimal digits is a common value (the 64 bit IEEE format).
It is typical that simple decimal fractions like 0.1 or 0.7 cannot be converted into their internal binary counterparts without a small loss of precision. This can lead to confusing results: for example, floor((0.1+0.7)*10) will usually return 7 instead of the expected 8, since the internal representation will be something like 7.9.
This is due to the fact that it is impossible to express some fractions in decimal notation with a finite number of digits. For instance, 1/3 in decimal form becomes 0.3.
So never trust floating number results to the last digit, and never compare floating point numbers for equality. If higher precision is necessary, the arbitrary precision math functions and gmp functions are available.
For information on converting strings to float, see String conversion to numbers. For values of other types, the conversion is performed by converting the value to integer first and then to float. See Converting to integer for more information. As of PHP 5, a notice is thrown if an object is converted to float.
A string is series of characters. Before PHP 6, a character is the same as a byte. That is, there are exactly 256 different characters possible. This also implies that PHP has no native support of Unicode. See utf8_encode() and utf8_decode() for some basic Unicode functionality.
Nota: It is no problem for a string to become very large. PHP imposes no boundary on the size of a string; the only limit is the available memory of the computer on which PHP is running.
A string literal can be specified in four different ways:
The simplest way to specify a string is to enclose it in single quotes (the character ').
To specify a literal single quote, escape it with a backslash (\). To specify a literal backslash before a single quote, or at the end of the string, double it (\\). Note that attempting to escape any other character will print the backslash too.
Nota: Unlike the two other syntaxes, variables and escape sequences for special characters will not be expanded when they occur in single quoted strings.
<?php
echo 'this is a simple string';
echo 'You can also have embedded newlines in
strings this way as it is
okay to do';
// Outputs: Arnold once said: "I'll be back"
echo 'Arnold once said: "I\'ll be back"';
// Outputs: You deleted C:\*.*?
echo 'You deleted C:\\*.*?';
// Outputs: You deleted C:\*.*?
echo 'You deleted C:\*.*?';
// Outputs: This will not expand: \n a newline
echo 'This will not expand: \n a newline';
// Outputs: Variables do not $expand $either
echo 'Variables do not $expand $either';
?>
If the string is enclosed in double-quotes ("), PHP will interpret more escape sequences for special characters:
| Sequence | Meaning |
|---|---|
| \n | linefeed (LF or 0x0A (10) in ASCII) |
| \r | carriage return (CR or 0x0D (13) in ASCII) |
| \t | horizontal tab (HT or 0x09 (9) in ASCII) |
| \v | vertical tab (VT or 0x0B (11) in ASCII) (since PHP 5.2.5) |
| \f | form feed (FF or 0x0C (12) in ASCII) (since PHP 5.2.5) |
| \\ | backslash |
| \$ | dollar sign |
| \" | double-quote |
| \[0-7]{1,3} | the sequence of characters matching the regular expression is a character in octal notation |
| \x[0-9A-Fa-f]{1,2} | the sequence of characters matching the regular expression is a character in hexadecimal notation |
As in single quoted strings, escaping any other character will result in the backslash being printed too. Before PHP 5.1.1, the backslash in \{$var} was not been printed.
The most important feature of double-quoted strings is the fact that variable names will be expanded. See string parsing for details.
A third way to delimit strings is the heredoc syntax: <<<. After this operator, an identifier is provided, then a newline. The string itself follows, and then the same identifier again to close the quotation.
The closing identifier must begin in the first column of the line. Also, the identifier must follow the same naming rules as any other label in PHP: it must contain only alphanumeric characters and underscores, and must start with a non-digit character or underscore.
It is very important to note that the line with the closing identifier must contain no other characters, except possibly a semicolon (;). That means especially that the identifier may not be indented, and there may not be any spaces or tabs before or after the semicolon. It's also important to realize that the first character before the closing identifier must be a newline as defined by the local operating system. This is \n on UNIX systems, including Mac OS X. The closing delimiter (possibly followed by a semicolon) must also be followed by a newline.
If this rule is broken and the closing identifier is not "clean", it will not be considered a closing identifier, and PHP will continue looking for one. If a proper closing identifier is not found before the end of the current file, a parse error will result at the last line.
Heredocs can not be used for initializing class members. Use nowdocs instead.
Example #1 Invalid example
<?php
class foo {
public $bar = <<<EOT
bar
EOT;
}
?>
Heredoc text behaves just like a double-quoted string, without the double quotes. This means that quotes in a heredoc do not need to be escaped, but the escape codes listed above can still be used. Variables are expanded, but the same care must be taken when expressing complex variables inside a heredoc as with strings.
Example #2 Heredoc string quoting example
<?php
$str = <<<EOD
Example of string
spanning multiple lines
using heredoc syntax.
EOD;
/* More complex example, with variables. */
class foo
{
var $foo;
var $bar;
function foo()
{
$this->foo = 'Foo';
$this->bar = array('Bar1', 'Bar2', 'Bar3');
}
}
$foo = new foo();
$name = 'MyName';
echo <<<EOT
My name is "$name". I am printing some $foo->foo.
Now, I am printing some {$foo->bar[1]}.
This should print a capital 'A': \x41
EOT;
?>
Il precedente esempio visualizzerà:
My name is "MyName". I am printing some foo. Now I am printing some Bar2. This should print a capital 'A': \x41
Nota: Heredoc support was added in PHP 4.
Nowdocs are to single-quoted strings what heredocs are to double-quoted strings. A nowdoc is specified similarly to a heredoc, but no parsing is done inside a nowdoc. The construct is ideal for embedding PHP code or other large blocks of text without the need for escaping. It shares some features in common with the SGML <![CDATA[ ]]> construct, in that it declares a block of text which is not for parsing.
A nowdoc is identified with the same <<< seqeuence used for heredocs, but the identifier which follows is enclosed in single quotes, e.g. <<<'EOT'. All the rules for heredoc identifiers also apply to nowdoc identifiers, especially those regarding the appearance of the closing identifier.
Example #3 Nowdoc string quoting example
<?php
$str = <<<'EOD'
Example of string
spanning multiple lines
using nowdoc syntax.
EOD;
/* More complex example, with variables. */
class foo
{
public $foo;
public $bar;
function foo()
{
$this->foo = 'Foo';
$this->bar = array('Bar1', 'Bar2', 'Bar3');
}
}
$foo = new foo();
$name = 'MyName';
echo <<<'EOT'
My name is "$name". I am printing some $foo->foo.
Now, I am printing some {$foo->bar[1]}.
This should not print a capital 'A': x41
EOT;
?>
Il precedente esempio visualizzerà:
My name is "$name". I am printing some $foo->foo. Now, I am printing some {$foo->bar[1]}. This should not print a capital 'A': \x41
Nota: Unlike heredocs, nowdocs can be used in any static data context. The typical example is initializing class members or constants:
Example #4 Static data example
<?php
class foo {
public $bar = <<<'EOT'
bar
EOT;
}
?>
Nota: Nowdoc support was added in PHP 5.3.0.
When a string is specified in double quotes or with heredoc, variables are parsed within it.
There are two types of syntax: a simple one and a complex one. The simple syntax is the most common and convenient. It provides a way to embed a variable, an array value, or an object property in a string with a minimum of effort.
The complex syntax was introduced in PHP 4, and can be recognised by the curly braces surrounding the expression.
If a dollar sign ($) is encountered, the parser will greedily take as many tokens as possible to form a valid variable name. Enclose the variable name in curly braces to explicitly specify the end of the name.
<?php
$beer = 'Heineken';
echo "$beer's taste is great"; // works; "'" is an invalid character for variable names
echo "He drank some $beers"; // won't work; 's' is a valid character for variable names
echo "He drank some ${beer}s"; // works
echo "He drank some {$beer}s"; // works
?>
Similarly, an array index or an object property can be parsed. With array indices, the closing square bracket (]) marks the end of the index. The same rules apply to object properties as to simple variables.
<?php
// These examples are specific to using arrays inside of strings.
// When outside of a string, always quote array string keys and do not use
// {braces}.
// Show all errors
error_reporting(E_ALL);
$fruits = array('strawberry' => 'red', 'banana' => 'yellow');
// Works, but note that this works differently outside a string
echo "A banana is $fruits[banana].";
// Works
echo "A banana is {$fruits['banana']}.";
// Works, but PHP looks for a constant named banana first, as described below.
echo "A banana is {$fruits[banana]}.";
// Won't work, use braces. This results in a parse error.
echo "A banana is $fruits['banana'].";
// Works
echo "A banana is " . $fruits['banana'] . ".";
// Works
echo "This square is $square->width meters broad.";
// Won't work. For a solution, see the complex syntax.
echo "This square is $square->width00 centimeters broad.";
?>
For anything more complex, you should use the complex syntax.
This isn't called complex because the syntax is complex, but because it allows for the use of complex expressions.
In fact, any value in the namespace can be included in a string with this syntax. Simply write the expression the same way as it would appeared outside the string, and then wrap it in { and }. Since { can not be escaped, this syntax will only be recognised when the $ immediately follows the {. Use {\$ to get a literal {$. Some examples to make it clear:
<?php
// Show all errors
error_reporting(E_ALL);
$great = 'fantastic';
// Won't work, outputs: This is { fantastic}
echo "This is { $great}";
// Works, outputs: This is fantastic
echo "This is {$great}";
echo "This is ${great}";
// Works
echo "This square is {$square->width}00 centimeters broad.";
// Works
echo "This works: {$arr[4][3]}";
// This is wrong for the same reason as $foo[bar] is wrong outside a string.
// In other words, it will still work, but only because PHP first looks for a
// constant named foo; an error of level E_NOTICE (undefined constant) will be
// thrown.
echo "This is wrong: {$arr[foo][3]}";
// Works. When using multi-dimensional arrays, always use braces around arrays
// when inside of strings
echo "This works: {$arr['foo'][3]}";
// Works.
echo "This works: " . $arr['foo'][3];
echo "This works too: {$obj->values[3]->name}";
echo "This is the value of the var named $name: {${$name}}";
echo "This is the value of the var named by the return value of getName(): {${getName()}}";
echo "This is the value of the var named by the return value of \$object->getName(): {${$object->getName()}}";
?>
Nota: Functions and method calls inside {$} work since PHP 5.
Characters within strings may be accessed and modified by specifying the zero-based offset of the desired character after the string using square array brackets, as in $str[42]. Think of a string as an array of characters for this purpose.
Nota: Strings may also be accessed using braces, as in $str{42}, for the same purpose. However, this syntax is deprecated as of PHP 6. Use square brackets instead.
Example #5 Some string examples
<?php
// Get the first character of a string
$str = 'This is a test.';
$first = $str[0];
// Get the third character of a string
$third = $str[2];
// Get the last character of a string.
$str = 'This is still a test.';
$last = $str[strlen($str)-1];
// Modify the last character of a string
$str = 'Look at the sea';
$str[strlen($str)-1] = 'e';
?>
Nota: Accessing variables of other types using [] or {} silently returns NULL.
Strings may be concatenated using the '.' (dot) operator. Note that the '+' (addition) operator will not work for this. See String operators for more information.
There are a number of useful functions for string manipulation.
See the string functions section for general functions, and the regular expression functions or the Perl-compatible regular expression functions for advanced find & replace functionality.
There are also functions for URL strings, and functions to encrypt/decrypt strings (mcrypt and mhash).
Finally, see also the character type functions.
A value can be converted to a string using the (string) cast or the strval() function. String conversion is automatically done in the scope of an expression where a string is needed. This happens when using the echo() or print() functions, or when a variable is compared to a string. The sections on Types and Type Juggling will make the following clearer. See also the settype() function.
A boolean TRUE value is converted to the string "1". Boolean FALSE is converted to "" (the empty string). This allows conversion back and forth between boolean and string values.
An integer or float is converted to a string representing the number textually (including the exponent part for floats). Floating point numbers can be converted using exponential notation (4.1E+6).
Nota: The decimal point character is defined in the script's locale (category LC_NUMERIC). See the setlocale() function.
Arrays are always converted to the string "Array"; because of this, echo() and print() can not by themselves show the contents of an array. To view a single element, use a construction such as echo $arr['foo']. See below for tips on viewing the entire contents.
Objects in PHP 4 are always converted to the string "Object". To print the values of object members for debugging reasons, read the paragraphs below. To get an object's class name, use the get_class() function. As of PHP 5, the __toString method is used when applicable.
Resources are always converted to strings with the structure "Resource id #1", where 1 is the unique number assigned to the resource by PHP at runtime. Do not rely upon this structure; it is subject to change. To get a resource's type, use the get_resource_type() function.
NULL is always converted to an empty string.
As stated above, directly converting an array, object, or resource to a string does not provide any useful information about the value beyond its type. See the functions print_r() and var_dump() for more effective means of inspecting the contents of these types.
Most PHP values can also be converted to strings for permanent storage. This method is called serialization, and is performed by the serialize() function. If the PHP engine was built with WDDX support, PHP values can also be serialized as well-formed XML text.
When a string is evaluated in a numeric context, the resulting value and type are determined as follows.
The string will be evaluated as a float if it contains any of the characters '.', 'e', or 'E'. Otherwise, it will be evaluated as an integer.
The value is given by the initial portion of the string. If the string starts with valid numeric data, this will be the value used. Otherwise, the value will be 0 (zero). Valid numeric data is an optional sign, followed by one or more digits (optionally containing a decimal point), followed by an optional exponent. The exponent is an 'e' or 'E' followed by one or more digits.
<?php
$foo = 1 + "10.5"; // $foo is float (11.5)
$foo = 1 + "-1.3e3"; // $foo is float (-1299)
$foo = 1 + "bob-1.3e3"; // $foo is integer (1)
$foo = 1 + "bob3"; // $foo is integer (1)
$foo = 1 + "10 Small Pigs"; // $foo is integer (11)
$foo = 4 + "10.2 Little Piggies"; // $foo is float (14.2)
$foo = "10.0 pigs " + 1; // $foo is float (11)
$foo = "10.0 pigs " + 1.0; // $foo is float (11)
?>
For more information on this conversion, see the Unix manual page for strtod(3).
To test any of the examples in this section, cut and paste the examples and insert the following line to see what's going on:
<?php
echo "\$foo==$foo; type is " . gettype ($foo) . "<br />\n";
?>
Do not expect to get the code of one character by converting it to integer, as is done in C. Use the ord() and chr() functions to convert between ASCII codes and characters.
An array in PHP is actually an ordered map. A map is a type that associates values to keys. This type is optimized for several different uses; it can be treated as an array, list (vector), hash table (an implementation of a map), dictionary, collection, stack, queue, and probably more. As array values can be other arrays, trees and multidimensional arrays are also possible.
Explanation of those data structures is beyond the scope of this manual, but at least one example is provided for each of them. For more information, look towards the considerable literature that exists about this broad topic.
An array can be created by the array() language construct. It takes as parameters any number of comma-separated key => value pairs.
array( key => value , ... ) // key may only be an integer or string // value may be any value of any type
<?php
$arr = array("foo" => "bar", 12 => true);
echo $arr["foo"]; // bar
echo $arr[12]; // 1
?>
A key may be either an integer or a string. If a key is the standard representation of an integer, it will be interpreted as such (i.e. "8" will be interpreted as 8, while "08" will be interpreted as "08"). Floats in key are truncated to integer. The indexed and associative array types are the same type in PHP, which can both contain integer and string indices.
A value can be any PHP type.
<?php
$arr = array("somearray" => array(6 => 5, 13 => 9, "a" => 42));
echo $arr["somearray"][6]; // 5
echo $arr["somearray"][13]; // 9
echo $arr["somearray"]["a"]; // 42
?>
If a key is not specified for a value, the maximum of the integer indices is taken and the new key will be that value plus 1. If a key that already has an assigned value is specified, that value will be overwritten.
<?php
// This array is the same as ...
array(5 => 43, 32, 56, "b" => 12);
// ...this array
array(5 => 43, 6 => 32, 7 => 56, "b" => 12);
?>
Before PHP 4.3.0, appending to an array in which the current maximum key was negative would create a new key as described above. Since PHP 4.3.0, the new key will be 0.
Using TRUE as key will evaluate to integer 1 as a key. Using FALSE as key will evaluate to integer 0 as a key. Using NULL as a key will evaluate to the empty string. Using the empty string as a key will create (or overwrite) a key with the empty string and its value; it is not the same as using empty brackets.
Arrays and objects can not be used as keys. Doing so will result in a warning: Illegal offset type.
An existing array can be modified by explicitly setting values in it.
This is done by assigning values to the array, specifying the key in brackets. The key can also be omitted, resulting in an empty pair of brackets ([]).
$arr[key] = value; $arr[] = value; // key may be an integer or string // value may be any value of any type
If $arr doesn't exist yet, it will be created, so this is also an alternative way to create an array. To change a certain value, assign a new value to that element using its key. To remove a key/value pair, call the unset() function on it.
<?php
$arr = array(5 => 1, 12 => 2);
$arr[] = 56; // This is the same as $arr[13] = 56;
// at this point of the script
$arr["x"] = 42; // This adds a new element to
// the array with key "x"
unset($arr[5]); // This removes the element from the array
unset($arr); // This deletes the whole array
?>
Nota: As mentioned above, if no key is specified, the maximum of the existing integer indices is taken, and the new key will be that maximum value plus 1. If no integer indices exist yet, the key will be 0 (zero). If a key that already has a value is specified, that value will be overwritten.
Note that the maximum integer key used for this need not currently exist in the array. It need only have existed in the array at some time since the last time the array was re-indexed. The following example illustrates:
<?php
// Create a simple array.
$array = array(1, 2, 3, 4, 5);
print_r($array);
// Now delete every item, but leave the array itself intact:
foreach ($array as $i => $value) {
unset($array[$i]);
}
print_r($array);
// Append an item (note that the new key is 5, instead of 0).
$array[] = 6;
print_r($array);
// Re-index:
$array = array_values($array);
$array[] = 7;
print_r($array);
?>Il precedente esempio visualizzerà:
Array ( [0] => 1 [1] => 2 [2] => 3 [3] => 4 [4] => 5 ) Array ( ) Array ( [5] => 6 ) Array ( [0] => 6 [1] => 7 )
There are quite a few useful functions for working with arrays. See the array functions section.
Nota: The unset() function allows removing keys from an array. Be aware that the array will not be reindexed. If a true "remove and shift" behavior is desired, the array can be reindexed using the array_values() function.
<?php
$a = array(1 => 'one', 2 => 'two', 3 => 'three');
unset($a[2]);
/* will produce an array that would have been defined as
$a = array(1 => 'one', 3 => 'three');
and NOT
$a = array(1 => 'one', 2 =>'three');
*/
$b = array_values($a);
// Now $b is array(0 => 'one', 1 =>'three')
?>
The foreach control structure exists specifically for arrays. It provides an easy way to traverse an array.
Always use quotes around a string literal array index. For example, $foo['bar'] is correct, while $foo[bar] is not. But why? It is common to encounter this kind of syntax in old scripts:
<?php
$foo[bar] = 'enemy';
echo $foo[bar];
// etc
?>
This is wrong, but it works. The reason is that this code has an undefined constant (bar) rather than a string ('bar' - notice the quotes). PHP may in future define constants which, unfortunately for such code, have the same name. It works because PHP automatically converts a bare string (an unquoted string which does not correspond to any known symbol) into a string which contains the bare string. For instance, if there is no defined constant named bar, then PHP will substitute in the string 'bar' and use that.
Nota: This does not mean to always quote the key. Do not quote keys which are constants or variables, as this will prevent PHP from interpreting them.
Il precedente esempio visualizzerà:<?php
error_reporting(E_ALL);
ini_set('display_errors', true);
ini_set('html_errors', false);
// Simple array:
$array = array(1, 2);
$count = count($array);
for ($i = 0; $i < $count; $i++) {
echo "\nChecking $i: \n";
echo "Bad: " . $array['$i'] . "\n";
echo "Good: " . $array[$i] . "\n";
echo "Bad: {$array['$i']}\n";
echo "Good: {$array[$i]}\n";
}
?>
Checking 0: Notice: Undefined index: $i in /path/to/script.html on line 9 Bad: Good: 1 Notice: Undefined index: $i in /path/to/script.html on line 11 Bad: Good: 1 Checking 1: Notice: Undefined index: $i in /path/to/script.html on line 9 Bad: Good: 2 Notice: Undefined index: $i in /path/to/script.html on line 11 Bad: Good: 2
More examples to demonstrate this behaviour:
<?php
// Show all errors
error_reporting(E_ALL);
$arr = array('fruit' => 'apple', 'veggie' => 'carrot');
// Correct
print $arr['fruit']; // apple
print $arr['veggie']; // carrot
// Incorrect. This works but also throws a PHP error of level E_NOTICE because
// of an undefined constant named fruit
//
// Notice: Use of undefined constant fruit - assumed 'fruit' in...
print $arr[fruit]; // apple
// This defines a constant to demonstrate what's going on. The value 'veggie'
// is assigned to a constant named fruit.
define('fruit', 'veggie');
// Notice the difference now
print $arr['fruit']; // apple
print $arr[fruit]; // carrot
// The following is okay, as it's inside a string. Constants are not looked for
// within strings, so no E_NOTICE occurs here
print "Hello $arr[fruit]"; // Hello apple
// With one exception: braces surrounding arrays within strings allows constants
// to be interpreted
print "Hello {$arr[fruit]}"; // Hello carrot
print "Hello {$arr['fruit']}"; // Hello apple
// This will not work, and will result in a parse error, such as:
// Parse error: parse error, expecting T_STRING' or T_VARIABLE' or T_NUM_STRING'
// This of course applies to using superglobals in strings as well
print "Hello $arr['fruit']";
print "Hello $_GET['foo']";
// Concatenation is another option
print "Hello " . $arr['fruit']; // Hello apple
?>
When error_reporting is set to show E_NOTICE level errors (by setting it to E_ALL, for example), such uses will become immediately visible. By default, error_reporting is set not to show notices.
As stated in the syntax section, what's inside the square brackets ('[' and ']') must be an expression. This means that code like this works:
<?php
echo $arr[somefunc($bar)];
?>
This is an example of using a function return value as the array index. PHP also knows about constants:
<?php
$error_descriptions[E_ERROR] = "A fatal error has occured";
$error_descriptions[E_WARNING] = "PHP issued a warning";
$error_descriptions[E_NOTICE] = "This is just an informal notice";
?>
Note that E_ERROR is also a valid identifier, just like bar in the first example. But the last example is in fact the same as writing:
<?php
$error_descriptions[1] = "A fatal error has occured";
$error_descriptions[2] = "PHP issued a warning";
$error_descriptions[8] = "This is just an informal notice";
?>
because E_ERROR equals 1, etc.
At some point in the future, the PHP team might want to add another constant or keyword, or a constant in other code may interfere. For example, it is already wrong to use the words empty and default this way, since they are reserved keywords.
Nota: To reiterate, inside a double-quoted string, it's valid to not surround array indexes with quotes so "$foo[bar]" is valid. See the above examples for details on why as well as the section on variable parsing in strings.
For any of the types: integer, float, string, boolean and resource, converting a value to an array results in an array with a single element with index zero and the value of the scalar which was converted. In other words, (array)$scalarValue is exactly the same as array($scalarValue).
If an object is converted to an array, the result is an array whose elements are the object's properties. The keys are the member variable names, with a few notable exceptions: private variables have the class name prepended to the variable name; protected variables have a '*' prepended to the variable name. These prepended values have null bytes on either side. This can result in some unexpected behaviour:
<?php
class A {
private $A; // This will become '\0A\0A'
}
class B extends A {
private $A; // This will become '\0B\0A'
public $AA; // This will become 'AA'
}
var_dump((array) new B());
?>
The above will appear to have two keys named 'AA', although one of them is actually named '\0A\0A'.
It is possible to compare arrays with the array_diff() function and with array operators.
The array type in PHP is very versatile. Here are some examples:
<?php
// this
$a = array( 'color' => 'red',
'taste' => 'sweet',
'shape' => 'round',
'name' => 'apple',
4 // key will be 0
);
// is completely equivalent with
$a['color'] = 'red';
$a['taste'] = 'sweet';
$a['shape'] = 'round';
$a['name'] = 'apple';
$a[] = 4; // key will be 0
$b[] = 'a';
$b[] = 'b';
$b[] = 'c';
// will result in the array array(0 => 'a' , 1 => 'b' , 2 => 'c'),
// or simply array('a', 'b', 'c')
?>
Example #1 Using array()
<?php
// Array as (property-)map
$map = array( 'version' => 4,
'OS' => 'Linux',
'lang' => 'english',
'short_tags' => true
);
// strictly numerical keys
$array = array( 7,
8,
0,
156,
-10
);
// this is the same as array(0 => 7, 1 => 8, ...)
$switching = array( 10, // key = 0
5 => 6,
3 => 7,
'a' => 4,
11, // key = 6 (maximum of integer-indices was 5)
'8' => 2, // key = 8 (integer!)
'02' => 77, // key = '02'
0 => 12 // the value 10 will be overwritten by 12
);
// empty array
$empty = array();
?>
Example #2 Collection
<?php
$colors = array('red', 'blue', 'green', 'yellow');
foreach ($colors as $color) {
echo "Do you like $color?\n";
}
?>
Il precedente esempio visualizzerà:
Do you like red? Do you like blue? Do you like green? Do you like yellow?
Changing the values of the array directly is possible since PHP 5 by passing them by reference. Before that, a workaround is necessary:
Example #3 Collection
<?php
// PHP 5
foreach ($colors as &$color) {
$color = strtoupper($color);
}
unset($color); /* ensure that following writes to
$color will not modify the last array element */
// Workaround for older versions
foreach ($colors as $key => $color) {
$colors[$key] = strtoupper($color);
}
print_r($colors);
?>
Il precedente esempio visualizzerà:
Array ( [0] => RED [1] => BLUE [2] => GREEN [3] => YELLOW )
This example creates a one-based array.
Example #4 One-based index
<?php
$firstquarter = array(1 => 'January', 'February', 'March');
print_r($firstquarter);
?>
Il precedente esempio visualizzerà:
Array ( [1] => 'January' [2] => 'February' [3] => 'March' )
Example #5 Filling an array
<?php
// fill an array with all items from a directory
$handle = opendir('.');
while (false !== ($file = readdir($handle))) {
$files[] = $file;
}
closedir($handle);
?>
Arrays are ordered. The order can be changed using various sorting functions. See the array functions section for more information. The count() function can be used to count the number of items in an array.
Example #6 Sorting an array
<?php
sort($files);
print_r($files);
?>
Because the value of an array can be anything, it can also be another array. This enables the creation of recursive and multi-dimensional arrays.
Example #7 Recursive and multi-dimensional arrays
<?php
$fruits = array ( "fruits" => array ( "a" => "orange",
"b" => "banana",
"c" => "apple"
),
"numbers" => array ( 1,
2,
3,
4,
5,
6
),
"holes" => array ( "first",
5 => "second",
"third"
)
);
// Some examples to address values in the array above
echo $fruits["holes"][5]; // prints "second"
echo $fruits["fruits"]["a"]; // prints "orange"
unset($fruits["holes"][0]); // remove "first"
// Create a new multi-dimensional array
$juices["apple"]["green"] = "good";
?>
Array assignment always involves value copying. It also means that the internal array pointer used by current() and similar functions is reset. Use the reference operator to copy an array by reference.
<?php
$arr1 = array(2, 3);
$arr2 = $arr1;
$arr2[] = 4; // $arr2 is changed,
// $arr1 is still array(2, 3)
$arr3 = &$arr1;
$arr3[] = 4; // now $arr1 and $arr3 are the same
?>
To create a new object, use the new statement to instantiate a class:
<?php
class foo
{
function do_foo()
{
echo "Doing foo.";
}
}
$bar = new foo;
$bar->do_foo();
?>
For a full discussion, see the Classes and Objects chapter.
If an object is converted to an object, it is not modified. If a value of any other type is converted to an object, a new instance of the stdClass built-in class is created. If the value was NULL, the new instance will be empty. Arrays convert to an object with properties named by keys, and corresponding values. For any other value, a member variable named scalar will contain the value.
<?php
$obj = (object) 'ciao';
echo $obj->scalar; // outputs 'ciao'
?>
A resource is a special variable, holding a reference to an external resource. Resources are created and used by special functions. See the appendix for a listing of all these functions and the corresponding resource types.
Nota: The resource type was introduced in PHP 4
See also the get_resource_type() function.
As resource variables hold special handlers to opened files, database connections, image canvas areas and the like, converting to a resource makes no sense.
Thanks to the reference-counting system introduced with PHP 4's Zend Engine, a resource with no more references to it is detected automatically, and it is freed by the garbage collector. For this reason, it is rarely necessary to free the memory manually.
Nota: Persistent database links are an exception to this rule. They are not destroyed by the garbage collector. See the persistent connections section for more information.
The special NULL value represents a variable with no value. NULL is the only possible value of type NULL.
Nota: The null type was introduced in PHP 4.
A variable is considered to be null if:
it has been assigned the constant NULL.
it has not been set to any value yet.
it has been unset().
mixed indicates that a parameter may accept multiple (but not necessarily all) types.
gettype() for example will accept all PHP types, while str_replace() will accept strings and arrays.
Some functions like call_user_func() or usort() accept user-defined callback functions as a parameter. Callback functions can not only be simple functions, but also object methods, including static class methods.
A PHP function is passed by its name as a string. Any built-in or user-defined function can be used, except language constructs such as: array(), echo(), empty(), eval(), exit(), isset(), list(), print() or unset().
A method of an instantiated object is passed as an array containing an object at index 0 and the method name at index 1.
Static class methods can also be passed without instantiating an object of that class by passing the class name instead of an object at index 0.
Apart from common user-defined function, create_function() can also be used to create an anonymous callback function.
Example #1 Callback function examples
<?php
// An example callback function
function my_callback_function() {
echo 'hello world!';
}
// An example callback method
class MyClass {
static function myCallbackMethod() {
echo 'Hello World!';
}
}
// Type 1: Simple callback
call_user_func('my_callback_function');
// Type 2: Static class method call
call_user_func(array('MyClass', 'myCallbackMethod'));
// Type 3: Object method call
$obj = new MyClass();
call_user_func(array($obj, 'myCallbackMethod'));
// Type 4: Static class method call (As of PHP 5.2.3)
call_user_func('MyClass::myCallbackMethod');
// Type 5: Relative static class method call (As of PHP 5.3.0)
class A {
public static function who() {
echo "A\n";
}
}
class B extends A {
public static function who() {
echo "B\n";
}
}
call_user_func(array('B', 'parent::who')); // A
?>
Nota: In PHP4, it was necessary to use a reference to create a callback that points to the actual object, and not a copy of it. For more details, see References Explained.
void as a return type means that the return value is useless. void in a parameter list means that the function doesn't accept any parameters.
$... in function prototypes means and so on. This variable name is used when a function can take an endless number of arguments.
PHP does not require (or support) explicit type definition in variable declaration; a variable's type is determined by the context in which the variable is used. That is to say, if a string value is assigned to variable $var, $var becomes a string. If an integer value is then assigned to $var, it becomes an integer.
An example of PHP's automatic type conversion is the addition operator '+'. If either operand is a float, then both operands are evaluated as floats, and the result will be a float. Otherwise, the operands will be interpreted as integers, and the result will also be an integer. Note that this does not change the types of the operands themselves; the only change is in how the operands are evaluated and what the type of the expression itself is.
<?php
$foo = "0"; // $foo is string (ASCII 48)
$foo += 2; // $foo is now an integer (2)
$foo = $foo + 1.3; // $foo is now a float (3.3)
$foo = 5 + "10 Little Piggies"; // $foo is integer (15)
$foo = 5 + "10 Small Pigs"; // $foo is integer (15)
?>
If the last two examples above seem odd, see String conversion to numbers.
To force a variable to be evaluated as a certain type, see the section on Type casting. To change the type of a variable, see the settype() function.
To test any of the examples in this section, use the var_dump() function.
Nota: The behaviour of an automatic conversion to array is currently undefined.
Also, because PHP supports indexing into strings via offsets using the same syntax as array indexing, the following example holds true for all PHP versions:
See the section titled String access by character for more information.<?php
$a = 'car'; // $a is a string
$a[0] = 'b'; // $a is still a string
echo $a; // bar
?>
Type casting in PHP works much as it does in C: the name of the desired type is written in parentheses before the variable which is to be cast.
<?php
$foo = 10; // $foo is an integer
$bar = (boolean) $foo; // $bar is a boolean
?>
The casts allowed are:
(binary) casting and b prefix forward support was added in PHP 5.2.1
Note that tabs and spaces are allowed inside the parentheses, so the following are functionally equivalent:
<?php
$foo = (int) $bar;
$foo = ( int ) $bar;
?>
Casting literal strings and variables to binary strings:
<?php
$binary = (binary)$string;
$binary = b"binary string";
?>
Nota: Instead of casting a variable to a string, it is also possible to enclose the variable in double quotes.
<?php
$foo = 10; // $foo is an integer
$str = "$foo"; // $str is a string
$fst = (string) $foo; // $fst is also a string
// This prints out that "they are the same"
if ($fst === $str) {
echo "they are the same";
}
?>
It may not be obvious exactly what will happen when casting between certain types. For more information, see these sections:
Variables in PHP are represented by a dollar sign followed by the name of the variable. The variable name is case-sensitive.
Variable names follow the same rules as other labels in PHP. A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. As a regular expression, it would be expressed thus: '[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*'
Nota: For our purposes here, a letter is a-z, A-Z, and the ASCII characters from 127 through 255 (0x7f-0xff).
Nota: $this is a special variable that can't be assigned.
Si può anche consultare Userland Naming Guide.
For information on variable related functions, see the Variable Functions Reference.
<?php
$var = 'Bob';
$Var = 'Joe';
echo "$var, $Var"; // outputs "Bob, Joe"
$4site = 'not yet'; // invalid; starts with a number
$_4site = 'not yet'; // valid; starts with an underscore
$täyte = 'mansikka'; // valid; 'ä' is (Extended) ASCII 228.
?>
By default, variables are always assigned by value. That is to say, when you assign an expression to a variable, the entire value of the original expression is copied into the destination variable. This means, for instance, that after assigning one variable's value to another, changing one of those variables will have no effect on the other. For more information on this kind of assignment, see the chapter on Expressions.
PHP also offers another way to assign values to variables: assign by reference. This means that the new variable simply references (in other words, "becomes an alias for" or "points to") the original variable. Changes to the new variable affect the original, and vice versa.
To assign by reference, simply prepend an ampersand (&) to the beginning of the variable which is being assigned (the source variable). For instance, the following code snippet outputs 'My name is Bob' twice:
<?php
$foo = 'Bob'; // Assign the value 'Bob' to $foo
$bar = &$foo; // Reference $foo via $bar.
$bar = "My name is $bar"; // Alter $bar...
echo $bar;
echo $foo; // $foo is altered too.
?>
One important thing to note is that only named variables may be assigned by reference.
<?php
$foo = 25;
$bar = &$foo; // This is a valid assignment.
$bar = &(24 * 7); // Invalid; references an unnamed expression.
function test()
{
return 25;
}
$bar = &test(); // Invalid.
?>
It is not necessary to initialize variables in PHP however it is a very good practice. Uninitialized variables have a default value of their type - FALSE, zero, empty string or an empty array.
Example #1 Default values of uninitialized variables
<?php
echo ($unset_bool ? "true" : "false"); // false
$unset_int += 25; // 0 + 25 => 25
echo $unset_string . "abc"; // "" . "abc" => "abc"
$unset_array[3] = "def"; // array() + array(3 => "def") => array(3 => "def")
?>
Relying on the default value of an uninitialized variable is problematic in the case of including one file into another which uses the same variable name. It is also a major security risk with register_globals turned on. E_NOTICE level error is issued in case of working with uninitialized variables, however not in the case of appending elements to the uninitialized array. isset() language construct can be used to detect if a variable has been already initialized.
PHP provides a large number of predefined variables to any script which it runs. Many of these variables, however, cannot be fully documented as they are dependent upon which server is running, the version and setup of the server, and other factors. Some of these variables will not be available when PHP is run on the command line. For a listing of these variables, please see the section on Reserved Predefined Variables.
In PHP 4.2.0 and later, the default value for the PHP directive register_globals is off. This is a major change in PHP. Having register_globals off affects the set of predefined variables available in the global scope. For example, to get DOCUMENT_ROOT you'll use $_SERVER['DOCUMENT_ROOT'] instead of $DOCUMENT_ROOT, or $_GET['id'] from the URL http://www.example.com/test.php?id=3 instead of $id, or $_ENV['HOME'] instead of $HOME.
For related information on this change, read the configuration entry for register_globals, the security chapter on Using Register Globals , as well as the PHP » 4.1.0 and » 4.2.0 Release Announcements.
Using the available PHP Reserved Predefined Variables, like the superglobal arrays, is preferred.
From version 4.1.0 onward, PHP provides an additional set of predefined arrays containing variables from the web server (if applicable), the environment, and user input. These new arrays are rather special in that they are automatically global--i.e., automatically available in every scope. For this reason, they are often known as "superglobals". (There is no mechanism in PHP for user-defined superglobals.) The superglobals are listed below; however, for a listing of their contents and further discussion on PHP predefined variables and their natures, please see the section Reserved Predefined Variables. Also, you'll notice how the older predefined variables ($HTTP_*_VARS) still exist. Dal PHP 5.0.0, gli array di variabili predefinite possono essere disabilitati con il parametro register_long_arrays .
Nota: Variable variables Superglobals cannot be used as variable variables inside functions or class methods.
Nota: Even though both the superglobal and HTTP_*_VARS can exist at the same time; they are not identical, so modifying one will not change the other.
If certain variables in variables_order are not set, their appropriate PHP predefined arrays are also left empty.
Since PHP 4.3.0, FILE information from $_FILES does not exist in $_REQUEST.
Nota: When running on the command line , this will not include the argv and argc entries; these are present in the $_SERVER array.
The scope of a variable is the context within which it is defined. For the most part all PHP variables only have a single scope. This single scope spans included and required files as well. For example:
<?php
$a = 1;
include 'b.inc';
?>
Here the $a variable will be available within the included b.inc script. However, within user-defined functions a local function scope is introduced. Any variable used inside a function is by default limited to the local function scope. For example:
<?php
$a = 1; /* global scope */
function Test()
{
echo $a; /* reference to local scope variable */
}
Test();
?>
This script will not produce any output because the echo statement refers to a local version of the $a variable, and it has not been assigned a value within this scope. You may notice that this is a little bit different from the C language in that global variables in C are automatically available to functions unless specifically overridden by a local definition. This can cause some problems in that people may inadvertently change a global variable. In PHP global variables must be declared global inside a function if they are going to be used in that function.
First, an example use of global:
Example #1 Using global
<?php
$a = 1;
$b = 2;
function Sum()
{
global $a, $b;
$b = $a + $b;
}
Sum();
echo $b;
?>
The above script will output "3". By declaring $a and $b global within the function, all references to either variable will refer to the global version. There is no limit to the number of global variables that can be manipulated by a function.
A second way to access variables from the global scope is to use the special PHP-defined $GLOBALS array. The previous example can be rewritten as:
Example #2 Using $GLOBALS instead of global
<?php
$a = 1;
$b = 2;
function Sum()
{
$GLOBALS['b'] = $GLOBALS['a'] + $GLOBALS['b'];
}
Sum();
echo $b;
?>
The $GLOBALS array is an associative array with the name of the global variable being the key and the contents of that variable being the value of the array element. Notice how $GLOBALS exists in any scope, this is because $GLOBALS is a superglobal. Here's an example demonstrating the power of superglobals:
Example #3 Example demonstrating superglobals and scope
<?php
function test_global()
{
// Most predefined variables aren't "super" and require
// 'global' to be available to the functions local scope.
global $HTTP_POST_VARS;
echo $HTTP_POST_VARS['name'];
// Superglobals are available in any scope and do
// not require 'global'. Superglobals are available
// as of PHP 4.1.0, and HTTP_POST_VARS is now
// deemed deprecated.
echo $_POST['name'];
}
?>
Another important feature of variable scoping is the static variable. A static variable exists only in a local function scope, but it does not lose its value when program execution leaves this scope. Consider the following example:
Example #4 Example demonstrating need for static variables
<?php
function Test()
{
$a = 0;
echo $a;
$a++;
}
?>
This function is quite useless since every time it is called it sets $a to 0 and prints "0". The $a++ which increments the variable serves no purpose since as soon as the function exits the $a variable disappears. To make a useful counting function which will not lose track of the current count, the $a variable is declared static:
Example #5 Example use of static variables
<?php
function Test()
{
static $a = 0;
echo $a;
$a++;
}
?>
Now, every time the Test() function is called it will print the value of $a and increment it.
Static variables also provide one way to deal with recursive functions. A recursive function is one which calls itself. Care must be taken when writing a recursive function because it is possible to make it recurse indefinitely. You must make sure you have an adequate way of terminating the recursion. The following simple function recursively counts to 10, using the static variable $count to know when to stop:
Example #6 Static variables with recursive functions
<?php
function Test()
{
static $count = 0;
$count++;
echo $count;
if ($count < 10) {
Test();
}
$count--;
}
?>
Nota: Static variables may be declared as seen in the examples above. Trying to assign values to these variables which are the result of expressions will cause a parse error.
Example #7 Declaring static variables
<?php
function foo(){
static $int = 0; // correct
static $int = 1+2; // wrong (as it is an expression)
static $int = sqrt(121); // wrong (as it is an expression too)
$int++;
echo $int;
}
?>
The Zend Engine 1, driving PHP 4, implements the static and global modifier for variables in terms of references. For example, a true global variable imported inside a function scope with the global statement actually creates a reference to the global variable. This can lead to unexpected behaviour which the following example addresses:
<?php
function test_global_ref() {
global $obj;
$obj = &new stdclass;
}
function test_global_noref() {
global $obj;
$obj = new stdclass;
}
test_global_ref();
var_dump($obj);
test_global_noref();
var_dump($obj);
?>
Executing this example will result in the following output:
NULL
object(stdClass)(0) {
}
A similar behaviour applies to the static statement. References are not stored statically:
<?php
function &get_instance_ref() {
static $obj;
echo 'Static object: ';
var_dump($obj);
if (!isset($obj)) {
// Assign a reference to the static variable
$obj = &new stdclass;
}
$obj->property++;
return $obj;
}
function &get_instance_noref() {
static $obj;
echo 'Static object: ';
var_dump($obj);
if (!isset($obj)) {
// Assign the object to the static variable
$obj = new stdclass;
}
$obj->property++;
return $obj;
}
$obj1 = get_instance_ref();
$still_obj1 = get_instance_ref();
echo "\n";
$obj2 = get_instance_noref();
$still_obj2 = get_instance_noref();
?>
Executing this example will result in the following output:
Static object: NULL
Static object: NULL
Static object: NULL
Static object: object(stdClass)(1) {
["property"]=>
int(1)
}
This example demonstrates that when assigning a reference to a static variable, it's not remembered when you call the &get_instance_ref() function a second time.
Sometimes it is convenient to be able to have variable variable names. That is, a variable name which can be set and used dynamically. A normal variable is set with a statement such as:
<?php
$a = 'hello';
?>
A variable variable takes the value of a variable and treats that as the name of a variable. In the above example, hello, can be used as the name of a variable by using two dollar signs. i.e.
<?php
$$a = 'world';
?>
At this point two variables have been defined and stored in the PHP symbol tree: $a with contents "hello" and $hello with contents "world". Therefore, this statement:
<?php
echo "$a ${$a}";
?>
produces the exact same output as:
<?php
echo "$a $hello";
?>
i.e. they both produce: hello world.
In order to use variable variables with arrays, you have to resolve an ambiguity problem. That is, if you write $$a[1] then the parser needs to know if you meant to use $a[1] as a variable, or if you wanted $$a as the variable and then the [1] index from that variable. The syntax for resolving this ambiguity is: ${$a[1]} for the first case and ${$a}[1] for the second.
Please note that variable variables cannot be used with PHP's Superglobal arrays within functions or class methods. The variable $this is also a special variable that cannot be referenced dynamically.
When a form is submitted to a PHP script, the information from that form is automatically made available to the script. There are many ways to access this information, for example:
Example #1 A simple HTML form
<form action="foo.php" method="post">
Name: <input type="text" name="username" /><br />
Email: <input type="text" name="email" /><br />
<input type="submit" name="submit" value="Submit me!" />
</form>
Depending on your particular setup and personal preferences, there are many ways to access data from your HTML forms. Some examples are:
Example #2 Accessing data from a simple POST HTML form
<?php
// Available since PHP 4.1.0
echo $_POST['username'];
echo $_REQUEST['username'];
import_request_variables('p', 'p_');
echo $p_username;
// Unavailable since PHP 6. As of PHP 5.0.0, these long predefined
// variables can be disabled with the register_long_arrays directive.
echo $HTTP_POST_VARS['username'];
// Available if the PHP directive register_globals = on. As of
// PHP 4.2.0 the default value of register_globals = off.
// Using/relying on this method is not preferred.
echo $username;
?>
Using a GET form is similar except you'll use the appropriate GET predefined variable instead. GET also applies to the QUERY_STRING (the information after the '?' in a URL). So, for example, http://www.example.com/test.php?id=3 contains GET data which is accessible with $_GET['id']. See also $_REQUEST and import_request_variables().
Nota: Superglobal arrays, like $_POST and $_GET, became available in PHP 4.1.0
As shown, before PHP 4.2.0 the default value for register_globals was on. The PHP community is encouraging all to not rely on this directive as it's preferred to assume it's off and code accordingly.
Nota: The magic_quotes_gpc configuration directive affects Get, Post and Cookie values. If turned on, value (It's "PHP!") will automagically become (It\'s \"PHP!\"). Escaping is needed for DB insertion. See also addslashes(), stripslashes() and magic_quotes_sybase.
PHP also understands arrays in the context of form variables (see the related faq). You may, for example, group related variables together, or use this feature to retrieve values from a multiple select input. For example, let's post a form to itself and upon submission display the data:
Example #3 More complex form variables
<?php
if ($_POST) {
echo '<pre>';
echo htmlspecialchars(print_r($_POST, true));
echo '</pre>';
}
?>
<form action="" method="post">
Name: <input type="text" name="personal[name]" /><br />
Email: <input type="text" name="personal[email]" /><br />
Beer: <br />
<select multiple name="beer[]">
<option value="warthog">Warthog</option>
<option value="guinness">Guinness</option>
<option value="stuttgarter">Stuttgarter Schwabenbräu</option>
</select><br />
<input type="submit" value="submit me!" />
</form>
When submitting a form, it is possible to use an image instead of the standard submit button with a tag like:
<input type="image" src="image.gif" name="sub" />
When the user clicks somewhere on the image, the accompanying form will be transmitted to the server with two additional variables, sub_x and sub_y. These contain the coordinates of the user click within the image. The experienced may note that the actual variable names sent by the browser contains a period rather than an underscore, but PHP converts the period to an underscore automatically.
Typically, PHP does not alter the names of variables when they are passed into a script. However, it should be noted that the dot (period, full stop) is not a valid character in a PHP variable name. For the reason, look at it:
<?php
$varname.ext; /* invalid variable name */
?>
For this reason, it is important to note that PHP will automatically replace any dots in incoming variable names with underscores.
Because PHP determines the types of variables and converts them (generally) as needed, it is not always obvious what type a given variable is at any one time. PHP includes several functions which find out what type a variable is, such as: gettype(), is_array(), is_float(), is_int(), is_object(), and is_string(). See also the chapter on Types.
Una costante è un identificatore (nome) per un valore. Come si può intuire, tale valore non può cambiare durante l'esecuzione dello script (fanno eccezione le costanti magiche, che, in realtà, non sono costanti). Una costante è "case-sensitive" per default. È convenzione comune che i nomi di costante siano sempre maiuscoli.
In PHP il nome di una costante segue le regole di qualsiasi "etichetta". Un nome di costante valido inizia con una lettera o underscore, seguita da un numero qualsiasi di caratteri alfanumerici o underscore. L'espressione regolare che esprime questa convenzione è: [a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*
Example #1 Nomi di costanti validi ed errati
<?php
// Nomi validi
define("FOO", "something");
define("FOO2", "something else");
define("FOO_BAR", "something more")
// Nomi di costante errati
define("2FOO", "something");
// Nomi validi, ma da evitare:
// un domani potrebbero essere utilizzati dal PHP per fornire costanti magiche
// e quindi si avrebbero problemi nello script
define("__FOO__", "something");
?>
Nota: In questo contesto una lettera è a-z, A-Z e i caratteri ASCII dal 127 al 255 (0x7f-0xff).
Come le superglobals, costante è sempre globale. Si può accedere alle costanti da qualsiasi punto dello script senza tenere conto della visibilità. Per maggiori dettagli sulla visibilità, leggere la sezione variable scope.
È possibile definire una variabile utilizzando la funzione define(). Una volta definita, a una costante non è possibile cambiare il valore o eliminarla.
Le costanti possono contenere solo dati di tipo scalare (boolean, integer, float e string).
Per ottenere il valore di una costante è sufficiente specificarne il nome. A differenza delle variabili, non è necessario anteporre il simbolo $ al nome di una variabile. Si può anche utilizzare la funzione constant(), per leggere il valore di una costante, nel caso in cui se ne ottenga dinamicamente il nome. Si utilizzi get_defined_constants() per ottenere una lista delle variabili definite.
Nota: Costanti e variabili (globali) si trovano in un "namespace" differente. Questo implica che generalmente TRUE e $TRUE sono differenti.
Se si utilizza il nome di una costante che non è definita, PHP assume che detto valore sia il nome della costante stessa, come se si fosse inserito il testo nel nome . Quando ciò accade PHP segnala il problema con un E_NOTICE. Vedere anche il capitolo del manuale sul perchè $foo[bar] è errata (a meno che prima non definisca bar come costante con define()). Per sapere se una costante è definita, si può utilizzare la funzione defined().
Di seguito sono riportate le principali differenze rispetto le variabili:
Example #2 Definizione di costanti
<?php
define("COSTANTE", "Ciao mondo.");
echo COSTANTE; // stampa "Ciao mondo."
echo Costante; // stampa "Costante" e genera una notice.
?>
Il PHP mette a disposizione ad ogni script diverse costanti predefinite disponibili a tutti gli script. Alcune di queste, tuttavia, sono create dai vari moduli, e, pertanto, saranno disponibili solo quando questi moduli sono caricati, sia dinamicamente sia staticamente.
Esistono cinque costanti magiche il cui valore cambia in base al contesto in cui sono utilizzate. Ad esempio, il valore di __LINE__ dipende da quale linea si trova nel momento in cui è richiamata. Queste costanti speciali sono 'case-insensitive' e sono:
| Nome | Descrizione |
|---|---|
| __LINE__ | Il numero di linea corrente. |
| __FILE__ | Il nome e percorso assoluto del file. Se viene utilizzata all'interno di un'include, la costante restituisce il nome del file incluso. Dal PHP 4.0.2, __FILE__ contiene sempre il percorso assoluto del file, mentre nelle versioni precedenti, in base alle circostanze, poteva contenere il percorso relativo. |
| __FUNCTION__ | Nome della funzione. (Aggiunta nel PHP 4.3.0.) Dal PHP 5 questa costante restituisce il nome della funzione così come è stato dichiarato (rispettando le lettere maiuscole). In PHP 4 è sempre minuscolo. |
| __CLASS__ | Nome della classe. (Aggiunta nel PHP 4.3.0.). Dal PHP 5 questa costante restituisce il nome della classe così come è stato dichiarato (rispettando le lettere maiuscole). In PHP 4 è sempre minuscolo. |
| __METHOD__ | Nome del metodo della classe. (Aggiunta nel PHP 5.0.0.). Questa costante restituisce il nome del metodo così come è stato dichiarato (rispettando le lettere maiuscole). |
Vedere anche get_class(), get_object_vars(), file_exists() e function_exists().
Expressions are the most important building stones of PHP. In PHP, almost anything you write is an expression. The simplest yet most accurate way to define an expression is "anything that has a value".
The most basic forms of expressions are constants and variables. When you type "$a = 5", you're assigning '5' into $a. '5', obviously, has the value 5, or in other words '5' is an expression with the value of 5 (in this case, '5' is an integer constant).
After this assignment, you'd expect $a's value to be 5 as well, so if you wrote $b = $a, you'd expect it to behave just as if you wrote $b = 5. In other words, $a is an expression with the value of 5 as well. If everything works right, this is exactly what will happen.
Slightly more complex examples for expressions are functions. For instance, consider the following function:
<?php
function foo ()
{
return 5;
}
?>
Assuming you're familiar with the concept of functions (if you're not, take a look at the chapter about functions), you'd assume that typing $c = foo() is essentially just like writing $c = 5, and you're right. Functions are expressions with the value of their return value. Since foo() returns 5, the value of the expression 'foo()' is 5. Usually functions don't just return a static value but compute something.
Of course, values in PHP don't have to be integers, and very often they aren't. PHP supports four scalar value types: integer values, floating point values (float), string values and boolean values (scalar values are values that you can't 'break' into smaller pieces, unlike arrays, for instance). PHP also supports two composite (non-scalar) types: arrays and objects. Each of these value types can be assigned into variables or returned from functions.
PHP takes expressions much further, in the same way many other languages do. PHP is an expression-oriented language, in the sense that almost everything is an expression. Consider the example we've already dealt with, '$a = 5'. It's easy to see that there are two values involved here, the value of the integer constant '5', and the value of $a which is being updated to 5 as well. But the truth is that there's one additional value involved here, and that's the value of the assignment itself. The assignment itself evaluates to the assigned value, in this case 5. In practice, it means that '$a = 5', regardless of what it does, is an expression with the value 5. Thus, writing something like '$b = ($a = 5)' is like writing '$a = 5; $b = 5;' (a semicolon marks the end of a statement). Since assignments are parsed in a right to left order, you can also write '$b = $a = 5'.
Another good example of expression orientation is pre- and post-increment and decrement. Users of PHP and many other languages may be familiar with the notation of variable++ and variable--. These are increment and decrement operators. In PHP/FI 2, the statement '$a++' has no value (is not an expression), and thus you can't assign it or use it in any way. PHP enhances the increment/decrement capabilities by making these expressions as well, like in C. In PHP, like in C, there are two types of increment - pre-increment and post-increment. Both pre-increment and post-increment essentially increment the variable, and the effect on the variable is identical. The difference is with the value of the increment expression. Pre-increment, which is written '++$variable', evaluates to the incremented value (PHP increments the variable before reading its value, thus the name 'pre-increment'). Post-increment, which is written '$variable++' evaluates to the original value of $variable, before it was incremented (PHP increments the variable after reading its value, thus the name 'post-increment').
A very common type of expressions are comparison expressions. These expressions evaluate to either FALSE or TRUE. PHP supports > (bigger than), >= (bigger than or equal to), == (equal), != (not equal), < (smaller than) and <= (smaller than or equal to). The language also supports a set of strict equivalence operators: === (equal to and same type) and !== (not equal to or not same type). These expressions are most commonly used inside conditional execution, such as if statements.
The last example of expressions we'll deal with here is combined operator-assignment expressions. You already know that if you want to increment $a by 1, you can simply write '$a++' or '++$a'. But what if you want to add more than one to it, for instance 3? You could write '$a++' multiple times, but this is obviously not a very efficient or comfortable way. A much more common practice is to write '$a = $a + 3'. '$a + 3' evaluates to the value of $a plus 3, and is assigned back into $a, which results in incrementing $a by 3. In PHP, as in several other languages like C, you can write this in a shorter way, which with time would become clearer and quicker to understand as well. Adding 3 to the current value of $a can be written '$a += 3'. This means exactly "take the value of $a, add 3 to it, and assign it back into $a". In addition to being shorter and clearer, this also results in faster execution. The value of '$a += 3', like the value of a regular assignment, is the assigned value. Notice that it is NOT 3, but the combined value of $a plus 3 (this is the value that's assigned into $a). Any two-place operator can be used in this operator-assignment mode, for example '$a -= 5' (subtract 5 from the value of $a), '$b *= 7' (multiply the value of $b by 7), etc.
There is one more expression that may seem odd if you haven't seen it in other languages, the ternary conditional operator:
<?php
$first ? $second : $third
?>
If the value of the first subexpression is TRUE (non-zero), then the second subexpression is evaluated, and that is the result of the conditional expression. Otherwise, the third subexpression is evaluated, and that is the value.
The following example should help you understand pre- and post-increment and expressions in general a bit better:
<?php
function double($i)
{
return $i*2;
}
$b = $a = 5; /* assign the value five into the variable $a and $b */
$c = $a++; /* post-increment, assign original value of $a
(5) to $c */
$e = $d = ++$b; /* pre-increment, assign the incremented value of
$b (6) to $d and $e */
/* at this point, both $d and $e are equal to 6 */
$f = double($d++); /* assign twice the value of $d before
the increment, 2*6 = 12 to $f */
$g = double(++$e); /* assign twice the value of $e after
the increment, 2*7 = 14 to $g */
$h = $g += 10; /* first, $g is incremented by 10 and ends with the
value of 24. the value of the assignment (24) is
then assigned into $h, and $h ends with the value
of 24 as well. */
?>
Some expressions can be considered as statements. In this case, a statement has the form of 'expr' ';' that is, an expression followed by a semicolon. In '$b=$a=5;', $a=5 is a valid expression, but it's not a statement by itself. '$b=$a=5;' however is a valid statement.
One last thing worth mentioning is the truth value of expressions. In many events, mainly in conditional execution and loops, you're not interested in the specific value of the expression, but only care about whether it means TRUE or FALSE. The constants TRUE and FALSE (case-insensitive) are the two possible boolean values. When necessary, an expression is automatically converted to boolean. See the section about type-casting for details about how.
PHP provides a full and powerful implementation of expressions, and documenting it entirely goes beyond the scope of this manual. The above examples should give you a good idea about what expressions are and how you can construct useful expressions. Throughout the rest of this manual we'll write expr to indicate any valid PHP expression.
Un operatore è un qualcosa che si posiziona tra uno o più valori (od espressioni, in gergo tecnico) e produce un'altro valore (in modo tale che la costruzione stessa diventi a sua volta un'espressione). In questo modo si può considerare operatori le funzioni o costruzioni che restituiscono valori (tipo print), e quelle che non restituiscono nulla (come echo) possono essere considerate come altro tipo di funzione.
Esistono tre tipi di operatori. Una tipologia sono gli operatori unari, i quali richiedono un solo valore, ad esempio ! (l'operatore di negazione) oppure ++ (l'operatore di autoincremento). Nel secondo gruppo troviamo gli operatori binari; questi costituiscono la maggior parte degli operatori disponibili in PHP, un e elenco di questi è presente alla sezione Precednza degli operatori.
Il terzo gruppo è costituito dal operatore ternario: ?:. Questo si può utilizzare per selezionare un espressione tra due possibili, in base ad una terza; piuttosto che dovere scegliere tra due righe di istruzioni o diversi percorsi di esecuzione. Racchiudere l'operatore ternario tra parentesi tonde è una buona idea.
La precedenza di un operatore specifica come esso tenga legate assieme "strettamente" due espressioni. Per esempio, nell'espressione 1 + 5 * 3, la risposta è 16 e non 18 perché l'operatore di moltiplicazione ("*") ha una precedenza più alta rispetto all'operatore di addizione ("+"). Le parentesi possono essere usate per forzare la precedenza, se necessario. Per esempio: (1 + 5) * 3 viene valutata 18. Se la precedenza tra gli operatori è simile, si utilizza l'associazione da sinistra a destra.
La seguente tabella fornisce una lista della precedenza degli operatori con gli operatori a più alta precedenza elencati prima. Gli operatori presenti nella medesima linea hanno uguale precedenza, in questi casi la loro associativià decide l'ordine con cui sono valutati.
| Associatività | Operatori | Informazioni aggiuntive |
|---|---|---|
| non associativi | new | new |
| destra | [ | array() |
| destra | ! ~ ++ -- (int) (float) (string) (array) (object) @ | incremento/decremento |
| destra | ! ~ + - (int) (float) (string) (array) (object) @ | tipi |
| sinistra | * / % | operatori aritmetici |
| sinistra | + - . | operatori aritmetici e operatori su stringhe |
| sinistra | << >> | operatori sui bit |
| non associativi | < <= > >= | operatori di confronto |
| non associativi | == != === !== | operatori di confronto |
| sinistra | & | operatori sui bit e riferimenti |
| sinistra | ^ | operatori sui bit |
| sinistra | | | operatori sui bit |
| sinistra | && | operatori logici |
| sinistra | || | operatori logici |
| sinistra | ? : | Operatore ternario |
| sinistra | = += -= *= /= .= %= &= |= ^= ~= <<= >>= | operatori di assegnazione |
| sinistra | and | operatori logici |
| sinistra | xor | operatori logici |
| sinistra | or | operatori logici |
| sinistra | , | diversi usi |
L'associazione a sinistra indica che l'espressione viene valutata da sinistra verso destra, l'associazione destra indica il contrario.
Example #1 Associatività
<?php
$a = 3 * 3 % 5; // (3 * 3) % 5 = 4
$a = true ? 0 : true ? 1 : 2; // (true ? 0 : true) ? 1 : 2 = 2
$a = 1;
$b = 2;
$a = $b += 3; // $a = ($b += 3) -> $a = 5, $b = 5
?>
Nota: Sebbene ! abbia una maggiore pecedenza rispetto a =, il PHP cintinua a permetter espressioni tipo la seguente: if (!$a = foo()), in questo caso l'output di foo() viene inserito in $a.
Ricordate l'aritmetica di base dalla scuola? Questi funzionano proprio come quelli.
| Esempio | Nome | Risultato |
|---|---|---|
| -$a | Negazione | Opposto di $a. |
| $a + $b | Addizione | La somma di $a e $b. |
| $a - $b | Sottrazione | La differenza di $a e $b. |
| $a * $b | Moltiplicazione | il prodotto di $a e $b. |
| $a / $b | Divisione | Quoziente di $a e $b. |
| $a % $b | Modulo | Il resto di $a diviso da $b. |
L'operatore di divisione ("/") restituisce un valore float in ogni caso, anche se i due operandi sono interi (oppure stringhe che vengono convertite in interi).
Nota: Il resto $a % $b è negativo per $a negativo.
Vedere anche le pagine del manuale sulle funzioni matematiche.
L'operatore di base dell'assegnazione è "=". La vostra prima inclinazione potrebbe essere di pensare che ciò sia come "uguale a". No. Esso significa realmente che l'operando a sinistra assume il valore dell'espressione a destra (ciò significa, "assegna il valore a").
Il valore di un'espressione di assegnazione è il valore assegnato. Cioè il valore di "$a = 3" è 3. Questo vi permette di fare qualche trucchetto:
<?php
$a = ($b = 4) + 5; // $a è uguale a 9 ora, e $b è stato impostato a 4.
?>
In aggiunta all'operatore di base dell'assegnazione, ci sono gli "operatori combinati" per tutta l'aritmetica binaria e gli operatori di stringa che vi consentono di usare un valore in un'espressione e poi impostare il suo valore al risultato di quell'espressione. Per esempio:
<?php
$a = 3;
$a += 5; // imposta $a a 8, come se avessimo detto: $a = $a + 5;
$b = "Ciao ";
$b .= "Lì!"; // imposta $b a "Ciao Lì!", proprio come $b = $b . "Lì!";
?>
Notare che l'assegnazione copia la variabile originale alla nuova (assegnazione per valore), così i cambiamenti ad una non si verificheranno nell' altra. Ciò può anche avere rilevanza se avete bisogno di copiare qualcosa come un grande array in un ciclo molto stretto. Dal PHP 4 viene supportato l'assegnazione per riferimento, usando la sintassi $var = &$othervar;, ma ciò non è possibile in PHP 3. 'L'assegnazione per riferimento' vuol dire che entrambe le variabili finiscono con il puntare agli stessi dati, e nulla è copiato in nessun posto. Per ulteriori approfondimenti sui riferimenti, consultare References explained.
Gli operatori bitwise vi permettono di alterare bit specifici in posizione on oppure off. Se entrambi i parametri di sinistra e destra sono stringhe, l'operatore bitwise opererà sui caratteri ASCII della stringa.
<?php
echo 12 ^ 9; // L'output è '5'
echo "12" ^ "9"; // L'output è il carattere Backspace (ascii 8)
// ('1' (ascii 49)) ^ ('9' (ascii 57)) = #8
echo "hallo" ^ "hello"; // L'output è il valore ascii #0 #4 #0 #0 #0
// 'a' ^ 'e' = #4
?>
| Esempio | Nome | Risultato |
|---|---|---|
| $a & $b | And | Sono impostati ad ON i bit che sono ON sia in $a che in $b. |
| $a | $b | Or | Sono impostati ad ON i bit che sono ON in $a oppure in $b. |
| $a ^ $b | Xor | Sono impostati ad ON i bit che sono ON in $a oppure in $b na non quelli che sono entrambi ON. |
| ~ $a | Not | Sono impostati ad ON i bit che sono OFF in $a, e viceversa. |
| $a << $b | Shift left | Sposta i bit di $a a sinistra di $b passi (ogni passo significa "moltiplica per due") |
| $a >> $b | Shift right | Sposta i bit di $a a destra di $b passi (ogni passo significa "dividi per due") |
Non spostare a destra per più di 32 bit sui sistemi a 32 bit. Non spostare a sinistra nei casi in cui il risultato è un numero più lungo di 32 bit.
Gli operatori di confronto, come suggerisce il loro nome, permettono di confrontare due valori. Può essere interessante vedere la tabella di raffronto dei tipi, dato che mostra esempi di vari confronti tra i tipi di variabili.
| Esempio | Nome | Risultato |
|---|---|---|
| $a == $b | Uguale | TRUE se $a è uguale a $b. |
| $a === $b | Identico | TRUE se $a è uguale a $b, ed essi sono dello stesso tipo. (Dal PHP 4) |
| $a != $b | Diversi | TRUE se $a è diverso da $b. |
| $a <> $b | Diversi | TRUE se $a è diverso da $b. |
| $a !== $b | Non identici | TRUE se $a è diverso da $b, o se essi non sono dello stesso tipo. (Dal PHP 4) |
| $a < $b | Minore | TRUE se $a è strettamente minore di $b. |
| $a > $b | Maggiore | TRUE se $a è strettamente maggiore di $b. |
| $a <= $b | Minore o uguale | TRUE se $a è minore o uguale a $b. |
| $a >= $b | Maggiore o uguale | TRUE se $a è maggiore o uguale a $b. |
Se si confronta interi con stringhe, la stringa viene convertita in numero. Se si confronta due stringhe numeriche, queste vengono confrontate come interi. Queste regole valgono anche per l'istruzione switch.
<?php
var_dump(0 == "a"); // 0 == 0 -> true
var_dump("1" == "01"); // 1 == 1 -> true
switch ("a") {
case 0:
echo "0";
break;
case "a": // mai raggiunta perchè "a" è già riconosciuta come 0
echo "a";
break;
}
?>
Se i tipi di operarandi utilizzati differiscono, il confronto viene svolto nell'ordine indicato della seguente tabella.
| Tipo dell'operando 1 | Tipo dell'operando 2 | Risultato |
|---|---|---|
| null oppure string | string | Si converte NULL in "", confronto numerico o lessicale |
| bool oppure null | qualsiasi | Convertito in bool, FALSE < TRUE |
| object | object | Le classi predefinite possono avere la propria funzione di confronto, differenti classi non sono confrontabili, classi uguali - hanno le medesime proprietà di confronto delle matrici (PHP 4), pre il PHP 5 vedere qui per maggiori spiegazioni. |
| string, resource oppure number | string, resource oppure number | Stringhe e risorse sono converti in numeri, confronto matematico |
| array | array | La matrice con meno membri è più piccola, se la chiave dell'operando 1 non si trova nell'operando 2 allora le matrici non si possono confrontare, in altri casi il confronto avviene valore per valore (vedere l'esempio seguente) |
| array | qualsiasi | array è sempre più grande |
| object | qualsiasi | object è sempre più grande |
Example #1 Trascrizione del confronto standard tra matrici
<?php
// Le matrici vengono confrontate come illustrato in questa funzione
function standard_array_compare($op1, $op2)
{
if (count($op1) < count($op2)) {
return -1; // $op1 < $op2
} elseif (count($op1) > count($op2)) {
return 1; // $op1 > $op2
}
foreach ($op1 as $key => $val) {
if (!array_key_exists($key, $op2)) {
return null; // uncomparable
} elseif ($val < $op2[$key]) {
return -1;
} elseif ($val > $op2[$key]) {
return 1;
}
}
return 0; // $op1 == $op2
}
?>
Vedere anche strcasecmp(), strcmp(), Array operators, e la sezione del manuale su Types.
Un'altro operatore condizionale è l'operatore ternario "?:".
Example #2 Assegnazione di un valore di default
<?php
// Esempio di utilizzo dell'operatore ternario
$action = (empty($_POST['action'])) ? 'default' : $_POST['action'];
// La riga precedente è simile a
if (empty($_POST['action'])) {
$action = 'default';
} else {
$action = $_POST['action'];
}
?>
Nota: Si noti che l'operatore ternario è un'istruzione, e non viene valutato come variabile, ma come risultato di un'istruzione. Questo è importante da sapere nel caso si desideri restituire una variabile per riferimento. La riga return $var == 42 ? $a : $b; in una funzione che restituisce per riferimento non funzionerà e, nelle ultime versioni di PHP, genererà un warning.
PHP supporta un operatore di controllo dell'errore: il carattere at (@). Quando prefisso ad una espressione in PHP, qualunque messaggio di errore che potesse essere generato da quella espressione sarà ignorato.
Se la caratteristica track_errors è abilitata, qualsiasi messaggio di errore generato dall'espressione sarà salvato nella variabile globale $php_errormsg. Questa variabile sarà sovrascritta ad ogni errore, così controllatela subito se volete usarla.
<?php
/* Errore di file intenzionale */
$my_file = @file ('file_inesistente') or
die ("Apertura del file fallita: l'errore è '$php_errormsg'");
// questo funziona per qualsiasi espressione, non solo funzioni:
$value = @$cache[$key];
// non verrà generata una notifica se l'indice $key non esiste.
?>
Nota: L'operatore @ funziona solo sulle espressioni. Una semplice regola è: se potete prendere il valore di qualcosa, potete anteporre ad esso l'operatore @. Per esempio, potete anteporre esso a variabili, funzioni e chiamate ad include(), costanti, e così via. non potete anteporre esso a definizioni di funzioni o classi, o strutture condizionali come if e foreach, e così via.
Vedere anche error_reporting() e la sezione del manuale Gestione degli errori e funzioni di log.
Attualmente il prefisso operatore di controllo dell'errore "@" disabiliterà la restituzione di errori per errori critici che interromperanno l'esecuzione dello script. Tra le altre cose, questo significa che se state usando "@" per sopprimere errori da una certa funzione ed essa non è disponibile oppure è stata scritta male, lo script terminerà senza dare indicazioni sul perché.
PHP supporta un operatore di esecuzione: backticks (``). Notare che quelli non sono apostrofi! PHP cercherà di eseguire il contenuto dei backticks come comando di shell; sarà restituito l'output (i.e., non sarà semplicemente esportato come output; può essere assegnato ad una variabile). L'uso dell'operatore backtick è identico alla funzione shell_exec().
<?php
$output = `ls -al`;
echo "<pre>$output</pre>";
?>
Nota: L'operatore backtick è disabilitato quando è abilitata modalità sicura oppure quando è disabilitata shell_exec().
Vedere anche la sezione del manuale Funzioni per l'esecuzione di programmi, popen(), proc_open() e Utilizzo del PHP da linea di comando.
PHP supporta lo stile C degli operatori di pre- e post-incremento e decremento.
Nota: Gli operatori di incremento e decremento non agiscono sui valori boolean. Anche decrementare il valore NULL non ha effetti, ma incrementarlo darà come risultato 1.
| Esempio | Nome | Effetto |
|---|---|---|
| ++$a | Pre-incremento | Incrementa $a di una unità, inoltre restituisce $a. |
| $a++ | Post-incremento | Restituisce $a, inoltre incrementa $a di una unità. |
| --$a | Pre-decremento | Decrementa $a di una unità, inoltre restituisce $a. |
| $a-- | Post-decremento | Restituisce $a, inoltre decrementa $a di una unità. |
Qui c'è un semplice script di esempio:
<?php
echo "<h3>Postincrement</h3>";
$a = 5;
echo "Dovrebbe essere 5: " . $a++ . "<br />\n";
echo "Dovrebbe essere 6: " . $a . "<br />\n";
echo "<h3>Pre-incremento</h3>";
$a = 5;
echo "Dovrebbe essere 6: " . ++$a . "<br />\n";
echo "Dovrebbe essere 6: " . $a . "<br />\n";
echo "<h3>Post-decremento</h3>";
$a = 5;
echo "Dovrebbe essere 5: " . $a-- . "<br />\n";
echo "Dovrebbe essere 4: " . $a . "<br />\n";
echo "<h3>Pre-decremento</h3>";
$a = 5;
echo "Dovrebbe essere 4: " . --$a . "<br />\n";
echo "Dovrebbe essere 4: " . $a . "<br />\n";
?>
Il PHP segue le convenzioni di Perl e non del C quando tratta le operazioni matematiche sui caratteri. Ad esempio, in Perl 'Z'+1 restituisce 'AA', mentre in C 'Z'+1 restituisce '[' ( ord('Z') == 90, ord('[') == 91 ). Attenzione che le variabili con caratteri possono essere sommate e non sottratte.
Example #1 Operazioni aritmetiche su variabili stringa
<?php
$i = 'W';
for ($n=0; $n<6; $n++)
echo ++$i . "\n";
Il precedente esempio visualizzerà:
X Y Z AA AB AC
Incrementare o decrementare valori booleani non ha effetto.
| Esempio | Nome | Risultato |
|---|---|---|
| $a and $b | And | TRUE se entrambi $a e $b sono TRUE. |
| $a or $b | Or | TRUE se uno tra $a o $b è TRUE. |
| $a xor $b | Xor | TRUE se uno tra $a o $b è TRUE, ma non entrambi. |
| ! $a | Not | TRUE se $a non è TRUE. |
| $a && $b | And | TRUE se entrambi $a e $b sono TRUE. |
| $a || $b | Or | TRUE se uno tra $a o $b è TRUE. |
La ragione per le due differenti variazioni degli operatori "and" e "or" è che essi operano con differenti precedenze. (Vedere Precedenza degli operatori.)
Ci sono due operatori di stringa. Il primo è l'operatore di concatenazione ('.'), che restituisce la concatenazione dei suoi argomenti di destra e di sinistra. Il secondo è l'operatore di assegnazione concatenata ('.='), che accoda l'argomento sul lato destro all'argomento sul lato sinistro. Per favore consultare Operatori di assegnazione per maggiori informazioni.
<?php
$a = "Ciao ";
$b = $a . "Mondo!"; // ora $b contiene "Ciao Mondo!"
$a = "Ciao ";
$a .= "Mondo!"; // ora $a contiene "Ciao Mondo!"
?>
Vedere anche le sezioni Stringhe e Funzioni per le stringhe nel manuale.
| Esempio | Nome | Risultato |
|---|---|---|
| $a + $b | Unione | Unione di $a e $b. |
| $a == $b | Uguaglianza | TRUE se $a e $b hanno le stesse coppie di chiavi/valori. |
| $a === $b | Identità | TRUE se $a e $b hanno le stesse coppie di chiavi/valori nel medesimo ordine e dl medesimo tipo. |
| $a != $b | Disuguaglianza | TRUE se $a non è uguale a $b. |
| $a <> $b | Disuguaglianza | TRUE se $a non è uguale a $b. |
| $a !== $b | Non-identità | TRUE se $a non è identico a $b. |
L'operatore + aggiunge la matrice di destra a quella di sinistra, mentre le chiavi duplicate NON sono sovrascritte.
<?php
$a = array("a" => "apple", "b" => "banana");
$b = array("a" => "pear", "b" => "strawberry", "c" => "cherry");
$c = $a + $b; // Unione di $a e $b
echo "Union of \$a and \$b: \n";
var_dump($c);
$c = $b + $a; // Unione di $b e $a
echo "Union of \$b and \$a: \n";
var_dump($c);
?>
Union of $a and $b: array(3) { ["a"]=> string(5) "apple" ["b"]=> string(6) "banana" ["c"]=> string(6) "cherry" } Union of $b and $a: array(3) { ["a"]=> string(4) "pear" ["b"]=> string(10) "strawberry" ["c"]=> string(6) "cherry" }
Gli elementi di una matrice sono uguali nel confronto se hanno le stesse chiavi e gli stessi valori.
Example #1 Confrontare le matrici
<?php
$a = array("apple", "banana");
$b = array(1 => "banana", "0" => "apple");
var_dump($a == $b); // bool(true)
var_dump($a === $b); // bool(false)
?>
Vedere anche la sezione del manuale sulle Matrici e Funzioni per le matrici.
PHP ha un unico operatore di tipo: instanceof. instanceof è utilizzato per determinare se un dato oggetto appartiene ad una data classe di oggetti.
L'operatore instanceof è stato introdotto in PHP 5. Prima di questo si utilizzava is_a(), ma ora is_a() viene sconsigliato in favore di instanceof.
<?php
class A { }
class B { }
$thing = new A;
if ($thing instanceof A) {
echo 'A';
}
if ($thing instanceof B) {
echo 'B';
}
?>
Poichè $thing è un oggetto di tipo A, ma non di tipo B, sarà eseguito soltanto il blocco dipendente dal tipo A:
A
Vedere anche get_class() e is_a().
Qualsiasi script PHP è costituito da una serie di istruzioni. Una istruzione può essere un'assegnazione, una chiamata di funzione, un loop, una istruzione condizionale che non fa nulla (istruzione vuota). Le istruzioni terminano con un punto e virgola. Inoltre, le istruzioni si possono raggruppare in blocchi di istruzioni racchiudendole tra parentesi graffa. Un gruppo di istruzioni è, a sua volta, un'istruzione. Il presente capitolo descrive i differenti tipi di istruzioni.
Il costrutto if è una delle più importanti caratteristiche di qualsiasi linguaggio, incluso PHP. Permette l'esecuzione condizionata di frammenti di codice. La struttura di controllo if di PHP è simile a quella del linguaggio C:
<?php
if (expression)
istruzione
?>
Come descritto nella sezione sulle espressioni, espressione restiruirà il suo valore booleano. Se espressione vale TRUE, PHP eseguirà istruzione, e se essa vale FALSE - la ignorerà. Più informazioni riguardo i valori valutati FALSE possono essere trovati nella sezione 'Conversione in booleano' .
L'esempio che segue visualizzerà a è maggiore di b se $a sarà maggiore di $b:
<?php
if ($a > $b)
echo "a è maggiore di b";
?>
Spesso sarà necessario eseguire più di una istruzione condizionale. Naturalmente non è necessario, utilizzare una singola clausola if per ciascuna istruzione. Si possono raggruppare diverse istruzioni in un singolo gruppo di istruzioni. Per esempio, il codice che segue visualizzerà a è maggiore di b se $a è maggiore di $b, e successivamente assegnerà il valore della variabile $a alla variabile $b:
<?php
if ($a > $b) {
echo "a è maggiore di b";
$b = $a;
}
?>
Si possono annidare indefinitamente istruzioni if, la qual cosa fornisce piena flessibilità per l'esecuzione di istruzioni condizionali in diversi punti del programma.
Spesso è necessario eseguire un'istruzione se una proposizione è vera e un'altra istruzione se la proposizione è falsa. Per questo si usa la clausola else. else estende il costrutto if aggiungendo la possibilità di eseguire un'istruzione se l'espressione nel ramo if è FALSE. L'esempio che segue visualizzerà a è maggiore di b se $a è maggiore di $b e a NON è maggiore di b altrimenti:
<?php
if ($a > $b) {
echo "a è maggiore di b";
} else {
echo "a NON è maggiore di b";
}
?>
elseif, come è facile intuire, è una combinazione di if ed else. Analogamente ad else, estende if aggiungendo la possibilità di eseguire un'altra istruzione nel caso in cui l'espressione contenuta nel ramo if sia FALSE. Però, a differenza di else, si eseguirà l'istruzione alternativa solamente se l'espressione contenuta nel ramo elseif sarà TRUE. L'esempio che segue, visualizzerà a è maggiore di b, a è uguale a b oppure a è minore di b:
<?php
if ($a > $b) {
echo "a è maggiore di b";
} elseif ($a == $b) {
echo "a è uguale a b";
} else {
echo "a è minore di b";
}
?>
Nel medesimo blocco if possono essere presenti più di una clausola elseif. Verrà eseguita l'istruzione del primo ramo elseif la cui espressione sia TRUE. In PHP è possibile scrivere 'else if' (due parole) e il significato sarà lo stesso di 'elseif' (una sola parola). Il significato sintattico è leggermente differente (se si ha familiarità con il linguaggio C, esso ha lo stesso comportamento) però al lato pratico l'effetto è il medesimo.
L'istruzione di un ramo elseif verrà eseguita solo se l'espressione del ramo if e le espressioni dei rami elseif precedenti sono FALSE, e se l'espressione del ramo elseif è TRUE.
PHP offre una sintassi alternativa per alcune delle sue strutture di controllo; vale a dire, if, while, for, foreach e switch. Fondamentalmente la sintassi alternativa consiste nel sostituire la prima parentesi graffa con il carattere "duepunti" (:) e la seconda parentesi graffa con endif;, endwhile;, endfor;, endforeach;, oppure endswitch;, rispettivamente.
<?php if ($a == 5): ?>
a è uguale a 5
<?php endif; ?>
Nell'esempio precedente, il blocco HTML "a è uguale a 5" è incluso nel ramo if scritto utilizzando la sintassi alternativa. Il blocco HTML verrà visualizzato solamente se $a è uguale a 5.
La sintassi alternativa si applica anche ad else ed elseif. Nell'esempio che segue si mostra come utilizzare la sintassi alternativa nel caso di un if con elseif ed else:
<?php
if ($a == 5):
echo "a è uguale a 5";
echo "...";
elseif ($a == 6):
echo "a è uguale a 6";
echo "!!!";
else:
echo "a non è nè 5 nè 6";
endif;
?>
Il ciclo while è la forma di ciclo più semplice tra quelle possibili in PHP. Si comporta come la sua controparte nel linguaggio C. La forma di base di un ciclo while è la seguente:
while (espressione) istruzione
Il significato di un ciclo while è semplice. Istruisce l'interprete PHP perchè esegua l'istruzione (o le istruzioni) in esso racchiuse, ripetutamente, fintanto che l'espressione contenuta nella clausola while ha valore TRUE. Il valore dell'espressione viene verificato ogni volta che il ciclo si ripete (iterazione), così che anche se il valore dell'espressione cambia durante l'esecuzione dell'istruzione, il ciclo non termina fino all'iterazione successiva. Ovviamente, se l'espressione nella clausola while ha valore FALSE dall'inizio, l'istruzione racchiusa nel blocco non verrà eseguita nemmeno una volta.
Come nel caso della struttura di controllo if, si possono raggruppare più istruzioni nello medesimo ciclo while racchiudendo le istruzioni in parentesi graffa, oppure utilizzando la sintassi alternativa:
while (espressione):
istruzione
...
endwhile;
Gli esempi seguenti sono identici e entrambi visualizzano i numeri da 1 a 10:
<?php
/* esempio 1 */
$i = 1;
while ($i <= 10) {
echo $i++; /* Il valore visualizzato è il valore della
variabile $i prima dell'incremento
(post-incremento) */
}
/* esempio 2 */
$i = 1;
while ($i <= 10):
echo $i;
$i++;
endwhile;
?>
Il ciclo do-while è simile al ciclo while, con l'unica differenza che il valore dell'espressione viene controllato alla fine di ogni iterazione anzichè all'inizio. La differenza più importante rispetto a while è che la prima iterazione di un blocco do-while verrà sempre eseguita (il valore dell'espressione viene controllato alla fine del ciclo), mentre non sarà necessariamente eseguito in un ciclo while (il valore dell'espressione viene controllato all'inizio del ciclo, e se tale valore è FALSE dall'inizio, l'esecuzione del ciclo termina immediatamente).
È ammessa una sola sintassi per il ciclo do-while:
<?php
$i = 0;
do {
echo $i;
} while ($i > 0);
?>
Il ciclo precedente verrà eseguito un'unica volta, dal momento che alla prima iterazione, quando si controlla l'espressione, il suo valore sarà FALSE ($i non è maggiore di 0) e il ciclo di esecuzioni, termina.
Chi ha utilizzato il linguaggio C conosce probabilmente un'altro modo di utilizzare il ciclo do-while, che permette di terminare l'esecuzione delle istruzioni durante l'esecuzione stessa, utilizzando do-while(0), e usando l'istruzione break. Il codice che segue esemplifica questa possibilità:
<?php
do {
if ($i < 5) {
echo "i non è abbastanza grande";
break;
}
$i *= $factor;
if ($i < $minimum_limit) {
break;
}
echo "i è ok";
/* processa i */
} while (0);
?>
Non vi preoccupate se l'esempio non è sufficientemente chiaro. Si possono scrivere ottimi programmi PHP anche senza far ricorso a questa 'possibilità'.
Il ciclo for è il ciclo più complesso tra quelli disponibili in PHP. Si comporta come la sua controparte nel linguaggio C. La sintassi di un clico for è:
for (espressione1; espressione2; espressione3)
istruzione
Il valore della prima espressione (espressione1) viene verificato (eseguito) una sola volta incondizionatamente all'inizio del ciclo.
Ad ogni iterazione, si controlla il valore di espressione2. Se è TRUE, il ciclo prosegue e viene eseguita l'istruzione (o le istruzioni) contenuta nel blocco; se è FALSE, l'esecuzione del ciclo termina.
Al termine di ogni iterazione, si verifica (si esegue) il valore di espressione3.
Le due espressioni possono anche non essere presenti. Se non esiste espressione2 significa che il ciclo deve essere eseguito indefinitamente (PHP considera implicitamente che il suo valore è TRUE, come in C). Questa possibilità in fondo non è utile come può sembrare perchè obbliga a terminare il ciclo utilizzando l'istruzione break invece di utilizzare le espressioni booleane del ciclo for .
Si considerino gli esempi seguenti. In ciascun caso si visualizzeranno i numeri da 1 a 10:
<?php
/* esempio 1 */
for ($i = 1; $i <= 10; $i++) {
echo $i;
}
/* esempio 2 */
for ($i= 1; ; $i++) {
if ($i > 10) {
break;
}
echo $i;
}
/* esempio 3 */
$i = 1;
for (; ; ) {
if ($i > 10) {
break;
}
echo $i;
$i++;
}
/* esempio 4 */
for ($i = 1; $i <= 10; print $i, $i++) ;
?>
Naturalmente il primo esempio sembra il migliore (o forse il quarto), ma l'uso del ciclo for senza espressioni può essere utile in molti casi.
PHP offre una sintassi alternativa (con i "punto e virgola") per i cicli for.
for (espressione1; espressione2; espressione3): istruzione ... endfor;
PHP 4 (non PHP 3) permette l'uso della struttura di controllo foreach, alla stessa maniera del linguaggio Perl e altri. Ciò semplicemente fornisce una facile metodo per attraversare un array. foreach funziona solo con le matrici e genera un errore se si tenta di utilizzarlo con variabili di tipo diffente oppure non inizializzate. Esistono due possibili notazioni sintattiche; la seconda è un'utile estensione della prima:
foreach(array_expression as $value)
istruzione
foreach(array_expression as $key => $value) i
struzione
La prima attraversa l'array dato da array_expression. Ad ogni ciclo, si assegna il valore dell'elemento corrente a $value e il puntatore interno avanza di una posizione (in modo tale che al ciclo successivo l'elemento corrente sarà il successivo elemento dell'array).
La seconda esegue lo stesso ciclo con la differenza che il valore dell'indice corrente viene assegnato ad ogni ciclo, alla variabile $key.
Dal PHP sono anche possibili cicli sugli oggetti.
Nota: All'inizio dell'esecuzione di un ciclo foreach il puntatore interno viene automaticamente posizionato nella prima posizione. Questo significa che non è necessario utilizzare la funzione reset() prima di un ciclo foreach.
Nota: A meno che la matrice non sia per riferimento, foreach agisce su una copia e non sulla matrice stessa. Pertanto il puntatore dell'array originale non viene modificato come accade utilizzando la funzione each() e le modifiche agli elementi dell'array non appaiono nell'array originale. Tuttavia il puntatore interno della matrice originale viene avanzato durante l'elaborazione della matrice. Se si assume che il ciclo foreach giunga al termine, allorasi avrà che il puntatore interno della matrcie sarà al termine della matrice stessa.
Dal PHP 5 si può modificare facilmente gli elementi di una matrice anteponendo & a $value with &. Questo assegna un riferimento anzichè copiare il valore.Questo è possibile soltanto se l'array indicato può essere referenziato (ad esempio è una variabile).<?php
$arr = array(1, 2, 3, 4);
foreach ($arr as &$value) {
$value = $value * 2;
}
// $arr vale ora array(2, 4, 6, 8)
?>
Nota: foreach non offre la possibilità di annullare la generazione di messaggi d'errore utilizzando il carattere '@'.
Avete probabilmente notato che i due cicli seguenti sono identici da un punto di vista funzionale:
<?php
$arr = array("one", "two", "three");
reset ($arr);
while (list(, $value) = each ($arr)) {
echo "Valore: $value<br />\n";
}
foreach ($arr as $value) {
echo "Valore: $value<br />\n";
}
?>
<?php
$arr = array("one", "two", "three");
reset ($arr);
while (list($key, $value) = each ($arr)) {
echo "Chiave: $key; Valore: $value<br />\n";
}
foreach ($arr as $key => $value) {
echo "Chiave: $key; Valore: $value<br>\n";
}
?>
Di seguito, altri esempi per mostrare possibili utilizzi:
<?php
/* esempio 1 foreach: solo il valore */
$a = array(1, 2, 3, 17);
foreach ($a as $v) {
echo "Valore corrente di \$a: $v.\n";
}
/* esempio 2 foreach: valore (con la chiave stampata) */
$a = array(1, 2, 3, 17);
$i = 0; /* solo per un proposito illustrativo */
foreach ($a as $v) {
echo "\$a[$i] => $v.\n";
$i++;
}
/* esempio 3 foreach: chiave e valore */
$a = array(
"uno" => 1,
"due" => 2,
"tre" => 3,
"diciassette" => 17
);
foreach ($a as $k => $v) {
echo "\$a[$k] => $v.\n";
}
/* esempio 4 foreach: array multidimensionali */
$a = array();
$a[0][0] = "a";
$a[0][1] = "b";
$a[1][0] = "y";
$a[1][1] = "z";
foreach ($a as $v1) {
foreach ($v1 as $v2) {
echo "$v2\n";
}
}
/* esempio 5 foreach: array dinamici */
foreach (array(1, 2, 3, 4, 5) as $v) {
echo "$v\n";
}
?>
break termina l'esecuzione di una struttura for, foreach, while, do-while o switch.
break accetta un argomento opzionale che definisce, nel caso di cicli annidati, il livello del ciclo che è da interrompere.
<?php
$arr = array ('uno', 'due', 'tre', 'quattro', 'stop', 'cinque');
while (list (, $val) = each ($arr)) {
if ($val == 'stop') {
break; /* Qui si può anche usare 'break 1;'. */
}
echo "$val<br />\n";
}
/* Uso dell'argomento opzionale. */
$i = 0;
while (++$i) {
switch ($i) {
case 5:
echo "At 5<br />\n";
break 1; /* Interrompe solo awitch. */
case 10:
echo "At 10; quitting<br />\n";
break 2; /* Interrompe switch e while. */
default:
break;
}
}
?>
continue si utilizza per interrompere l'esecuzione del ciclo corrente e continuare con l'esecuzione dall'inizio del ciclo successivo dopo avere valutato la condizione.
Nota: Si noti che in PHP l'istruzione switch è considerata un'elemento di loop per gli scopi di continue.
continue accetta un argomento numerico opzionale che definisce, nel caso di cicli annidati, il numero di cicli da interrompere e da cui iniziare l'esecuzione dell'iterazione successiva.
<?php
while (list($key, $value) = each ($arr)) {
if (!($key % 2)) { // salta odd members
continue;
}
do_something_odd($value);
}
$i = 0;
while ($i++ < 5) {
echo "Esterno<br />\n";
while (1) {
echo " Centrale<br />\n";
while (1) {
echo " Interno<br />\n";
continue 3;
}
echo "Questo non sarà mai stampato.<br />\n";
}
echo "Nemmeno questo.<br />\n";
}
?>
L'omissione del punto e virgola dopo continue può creare confuzione. Nel sseguente esempio si illustra cosa non di deve fare.
<?php
for ($i = 0; $i < 5; ++$i) {
if ($i == 2)
continue
print "$i\n";
}
?>
Ci si può aspettare come risultato:
1 3 4
invece si avrà:
2
poichè il valore restituida da print() è int(1) e sembrerà il numero opzionale indicato in precedenza.
switch è simile a una serie di if sulla stessa espressione. In molti casi può essere necessario confrontare una variabile (o espressione) con differenti valori ed eseguire un differente blocco di istruzioni a seconda del valore di detta variabile. Questo è esattamente quello che fa la struttura di controllo switch.
Nota: Si noti che a differenza di altri linguaggi, l'istruzione continue si può utilizzare anche con switch ed ha un comportamento simile a break. Se si ha uno switch all'interno di un ciclo e si desidera continuare con il prossimo ciclo del loop esterno, utilizzare continue 2.
Gli esempi seguenti mostrano due maniere differenti di scrivere la stessa cosa, uno utilizzando una serie di istruzioni if ed elseif l'altro utilizzando switch:
Example #1 Struttura switch
<?php
if ($i == 0) {
echo "i è uguale a 0";
} elseif ($i == 1) {
echo "i è uguale a 1";
} elseif ($i == 2) {
echo "i è uguale a 2";
}
switch ($i) {
case 0:
echo "i è uguale a 0";
break;
case 1:
echo "i è uguale a 1";
break;
case 2:
echo "i è uguale a 2";
break;
}
?>
Example #2 L'istruzione switch permette l'uso di stringhe
<?php
switch ($i) {
case "apple":
echo "i is apple";
break;
case "bar":
echo "i is bar";
break;
case "cake":
echo "i is cake";
break;
}
?>
È importante comprendere esattamente come viene eseguita la clausola switch per evitare errori. Un'istruzione switch esegue linea dopo linea le istruzioni in essa contenuta. All'inizio non viene eseguito alcun codice. Solamente quando incontra una clausola case il cui valore è uguale al valore della viariabile, PHP inizia ad eseguire le istruzioni contenute nel blocco case. PHP continua l'esecuzione delle istruzioni fino alla termine del blocco switch, o quando incontra un'istruzione break. Se non esiste alcuna istruzione break al termine di un blocco case PHP continuerà l'esecuzione delle istruzioni del blocco case successivo. Per esempio:
<?php
switch ($i) {
case 0:
echo "i è uguale a 0";
case 1:
echo "i è uguale a 1";
case 2:
echo "i è uguale a 2";
}
?>
In questo caso se $i è uguale a 0, PHP eseguirà tutte le istruzioni echo!. Se $i è uguale a 1, PHP eseguirà le ultime due echo. Si sarebbe ottenuto il comportamento atteso ( visualizzazione di 'i uguale a 2') solamente se $i è uguale a 2. Pertanto è importante non dimenticare l'istruzione break (anche se in alcuni casi potrà essere necessario non utilizzarla).
In un'istruzione switch, la condizione in parentesi viene valutata una sola volta e il risultato viene confrontato con ciascun ramo case. Utilizzando elseif, la condizione viene valutata una seconda volta. Se tale condizione è più complessa di un semplice confronto e/o è in un ciclo piuttosto pesante, l'uso di switch dovrebbe garantire un minor tempo di esecuzione.
Un blocco case può anche non contenere istruzioni, nel qual caso il controllo passa semplicemente al successivo blocco case.
<?php
switch ($i) {
case 0:
case 1:
case 2:
print "i è minore di 3 ma non negativo";
break;
case 3:
print "i è 3";
}
?>
Un blocco case speciale è il il blocco case di default. Uguaglia tutte le condizioni non uguagliate nei blocchi case precedenti e dev'essere l'ultimo blocco case. Per esempio:
<?php
switch ($i) {
case 0:
echo "i è uguale a 0";
break;
case 1:
echo "i è uguale a 1";
break;
case 2:
echo "i è uguale a 2";
break;
default:
echo "i è diverso da 0, 1 o 2";
}
?>
L'espressione in un ramo case può essere qualsiasi espressione il cui valore sarà di tipo intero, decimale, numerico e stringa. Array e oggetti (objects) non sono ammessi a meno che non siano dereferenziati a un tipo di dato semplice tra quelli precedentemente elencati.
Come per altre strutture di controllo è possibile utilizzare una sintassi alternativa. Si veda Sintassi alternativa per le strutture di controllo per ulteriori esempi.
<?php
switch ($i):
case 0:
echo "i è uguale a 0";
break;
case 1:
echo "i è uguale a 1";
break;
case 2:
echo "i è uguale a 2";
break;
default:
echo "i è diverso da 0, 1 o 2";
endswitch;
?>
Il costrutto declare si usa per definire direttive di esecuzione per blocchi di istruzioni. La sintassi è simile alla sintassi di altre strutture di controllo:
declare (direttiva)
istruzione
La sezione direttiva permette di impostare il comportamento del blocco declare . Attualmente è riconosciuta una sola direttiva: la direttiva ticks. (Fare riferimento più in basso per ulteriori informazioni relative alla direttiva ticks)
Verrà eseguita la parte istruzione del blocco declare -- come verrà eseguita e quali effetti collaterali emergeranno durante l'esecuzione potrà dipendere dalla direttiva impostata nel blocco direttiva.
L'istruzione declare