Funzioni interne (built-in)
This may be of help to some. I was looking for a way to have a wrapper class with subclasses.
From the subclasses, I wanted to be able to call functions (and even pass arguments to those functions) from other subclasses, using the wrapper class as a bridge.
My solution:
---------------------
class parser
{
var $class;
function parser()
{
$this->class = array();
}
function LoadClass($className)
{
$this->class[$className] = new $className;
}
function RunFunction($className, $functionName, $functionArgs=array() )
{
call_user_func_array( array( &$this->class[$className], $functionName) , $functionArgs);
}
function GetVarValue($className, $varName)
{
return $this->class[$className][$varName];
}
}
class test
{
var $myvar;
var $name;
function test()
{
$this->myvar = 1;
$this->name = "Shaun";
}
function runme($name=null)
{
if ($name !== null)
{
echo "Hi " . $name;
}
else
{
echo "Hi " . $this->name;
}
}
}
class test2 extends parser
{
function runme()
{
parent::LoadClass("test");
parent::RunFunction("test", "runme", array("name" => "Bob") );
}
}
Usage:
-----------
$parser = new parser;
$test = new test;
$test2 = new test2;
$test2->runme(); // outputs Bob
Classi e Oggetti (PHP 4)
Indice dei contenuti
- extends
- Costruttori
- Operatore Scope Resolution (::)
- parent
- Serializzare oggetti - oggetti nelle sessioni
- Le funzioni magiche __sleep e __wakeup
- Riferimenti all'interno del costruttore
- Confronto di oggetti
Classi
Una classe è una collezione di variabili e funzioni che utilizzano queste variabili. Una classe si definisce usando la seguente sintassi:
<?php
class Cart {
var $items; // Articoli nel carrello
// Aggiunge $num articoli di $artnr nel carrello
function add_item ($artnr, $num) {
$this->items[$artnr] += $num;
}
// Prende $num articoli di $artnr e li rimuove dal carrello
function remove_item ($artnr, $num) {
if ($this->items[$artnr] > $num) {
$this->items[$artnr] -= $num;
return true;
} elseif ($this->items[$artnr] == $num) {
unset($this->items[$artnr]);
return true;
} else {
return false;
}
}
}
?>
Il codice definisce una classe chiamata Cart composta da un array associativo che archivia gli articoli nel carrello e due funzioni per aggiungere e rimuovere gli articoli dal carrello stesso.
Avviso
NON spezzate una definizione di classe in più file o in più blocchi PHP. Si può anche EVITARE di spezzare la definizione di una classe in più blocchi PHP, a meno che la suddivisione non sia all'interno della dichiarazione di un metodo. Il seguente codice non funziona:
<?php
class test {
?>
<?php
function test() {
print 'OK';
}
}
?>
Tuttavia è permessa la seguente struttura:
<?php
class test {
function test() {
?>
<?php
print 'OK';
}
}
?>
Le seguenti note cautelative sono valide per PHP 4.
Attenzione
Il nome stdClass è usato esclusivamente da Zend ed è riservato. Non è quindi possibile creare una classe chiamata stdClass in PHP.
Attenzione
I nomi di funzione __sleep e __wakeup sono riservati e magici nelle classi PHP. Non è possibile creare funzioni con questi nomi nelle classi definite dall'utente, a meno che non sia desiderata la funzionalità magica connessa a questi nomi. Si veda sotto per avere più informazioni.
Attenzione
PHP riserva tutti i nomi di funzione che iniziano con __ a funzioni magiche. Si suggerisce di non usare nomi di funzioni che utilizzano con i caratteri __ in PHP a meno che non si desideri implementare una funzionalità magica.
In PHP 4, sono permesse inizializzazioni di variabili con valori costanti solamente grazie all'uso di var. Per inizializzare variabili con valori non-costanti, bisogna creare una funzione d'inizializzazione che è chiamata automaticamente all'istanziazione di un oggetto da una classe. Questo tipo di funzione si chiama costruttore (vedi sotto).
<?php
class Cart {
/* questo non funziona in PHP 4. */
var $todays_date = date("Y-m-d");
var $name = $firstname;
var $owner = 'Fred ' . 'Jones';
/* E' permesso l'uso di matrici contenenti costanti */
var $items = array("VCR", "TV");
}
/* Questo è corretto. */
class Cart {
var $todays_date;
var $name;
var $owner;
var $items;
var $items = array("VCR", "TV");
function Cart() {
$this->todays_date = date("Y-m-d");
$this->name = $GLOBALS['firstname'];
/* etc ... */
}
}
?>
Le classi sono tipi del linguaggio, e sono modelli per variabili reali. Per creare una variabile oggetto si usa l'operatore new.
<?php
$cart = new Cart;
$cart->add_item("10", 1);
$another_cart = new Cart;
$another_cart->add_item("0815", 3);
?>
Il codice sopra, genera gli oggetti $cart e $another_cart, dalla classe Cart. La funzione add_item() dell'oggetto $cart è chiamata per aggiungere una ricorrenza dell'articolo numero 10 a $cart. Ad $another_cart sono aggiunte 3 ricorrenze dell'articolo numero 0815.
Sia $cart che $another_cart dispongono delle funzioni add_item(), remove_item() e della variabile $items, ma per ogni oggetto queste sono funzioni e variabili sono distinte. Potete pensare agli oggetti come a qualcosa di simile alle directories di un filesystem. In un filesystem si possono avere due diversi files README.TXT, purchè siano in directories differenti. Così come in un filesystem dovete digitare il nome (percorso) completo per raggiungere un determinato file partendo da una directory toplevel, così dovete specificare il nome completo di una funzione o variabile che desiderate richiamare da un oggetto. Per PHP, la directory toplevel è il namespace globale dell'oggetto ed il separatore del pathname (/) è ->. Così $cart->items e $another_cart->items sono due diverse variabili che differiscono per il nome. Si noti che la variabile si chiama $cart->items, e non $cart->$items, questo perchè le variabili il PHP si scrivono con un unico simbolo di dollaro.
<?php
// corretto con un singolo $
$cart->items = array("10" => 1);
// non valido, perchè $cart->$items diventa $cart->""
$cart->$items = array("10" => 1);
// corretto, ma non sempre può funzionare:
// $cart->$myvar diventa $cart->items
$myvar = 'items';
$cart->$myvar = array("10" => 1);
?>
Quando si definisce una classe, non è possibile prevedere quale nome avrà l'oggetto istanziato nel programma. Quando la classe Cart è stata scritta, non si poteva prevedere che l'oggetto istanziato da essa si sarebbe potuto chiamare $cart o $another_cart. Quindi non è possibile scrivere $cart->items all'interno della classe Cart in fase di progettazione. Per poter accedere alle funzioni e alle variabili interne di una classe perciò si usa la pseudo-variabile $this che può essere letta come 'la mia\il mio' o 'di questo oggetto'. Quindi, '$this->items[$artnr] += $num' può essere letto come 'aggiungi $num al contatore $artnr al del mio array degli articoli' o 'aggiungi $num al contatore $artnr dell'array degli articoli di questo oggetto'.
Nota: La pseudo variabile $this di norma non è definita se il metodo in cui è utilizzata è richiamato staticamente. Tuttavia questa non è la regola: $this è definita se il metodo è chiamato staticamente da un'altro oggetto. In questo caso il valore di $this è l'oggetto chiamante. Tutto ciò viene illustrato dal seguente esempio:
<?php
class A
{
function foo()
{
if (isset($this)) {
echo '$this is defined (';
echo get_class($this);
echo ")\n";
} else {
echo "\$this is not defined.\n";
}
}
}
class B
{
function bar()
{
A::foo();
}
}
$a = new A();
$a->foo();
A::foo();
$b = new B();
$b->bar();
B::bar();
?>Il precedente esempio visualizzerà:
$this is defined (a) $this is not defined. $this is defined (b) $this is not defined.
Nota: Ci sono molte utili funzioni per manipolare classi ed oggetti. Se desiderate conoscerle potete dare un'occhiata alle Class/Object Functions.
add a note
User Contributed NotesClassi e Oggetti (PHP 4)
simshaun at gmail dot com
03-Apr-2008 08:55
03-Apr-2008 08:55
me at igorthetroll dot com
22-Oct-2007 07:01
22-Oct-2007 07:01
A little expanssion on the original shopping cart example.
It may look inherit to advance class user but to a beginer it will be helpful.
<?php
class Cart {
var $items; // Items in our shopping cart
// Add $num articles of $artnr to the cart
function add_item($artnr, $num) {
$this->items[$artnr] += $num;
}
// Take $num articles of $artnr out of the cart
function remove_item($artnr, $num) {
if ($this->items[$artnr] > $num) {
$this->items[$artnr] -= $num;
return true;
} elseif ($this->items[$artnr] == $num) {
unset($this->items[$artnr]);
return true;
} else {
return false;
}
}
function print_item($artnr) {
$blah=$this->items[$artnr];
return $blah;
}
}
?>
<?php
$cart = new Cart;
$cart->add_item("10", 5);
$cart->add_item("10", 3);
$cart->remove_item("10", 1);
echo $cart->print_item("10");
$another_cart = new Cart;
$another_cart->add_item("0815", 3);
?>
Added a print_item() function that returns the number of items in the shopping cart class for a specific item, for later manipulation as a variable.
Aouie Web_Form_Aouie.net
27-Aug-2007 07:55
27-Aug-2007 07:55
class casting (type casting to an extended class) workaround. Useful to use functionality in an extended class on an instance of a base class (especially when the BaseClass file needs to be small and the extended class functions are huge). Tested to work on public, protected and private vars in PHP5.
---
class ABaseClass
{
private $T1;
protected $T2;
public $T3;
public function CopyFrom( )
{
// If this class had parents then you will want to implement and use parent::$CopyFrom( ). If not, then private members in the parent class will not be copied.
return get_object_vars( $this );
}
protected function CopyInto( $VarArr )
{
// If this class had parents then in order to copy the private values we must implement and use parent::CopyInto( $VarArr ).
$TempArr = get_class_vars( __CLASS__ );
foreach( $TempArr as $VarName => $Var1 )
{
$this->$VarName = $VarArr[ $VarName ];
}
}
}
class AnExtendedClass extends ABaseClass
{
public function __construct( $theBaseClassInstance )
{
$this->CopyInto( $theBaseClassInstance->CopyFrom( ) );
}
public function LongFunctionIntheFileWithTheExtendedClass( )
{
// Bla Bla Bla
}
}
---
$BaseInstance = new ABaseClass();
...
$ExtendedInstance = new AnExtendedClass( $BaseInstance );
$ExtendedInstance->LongFunctionIntheFileWithTheExtendedClass( );
skds1433 at gmail dot com
18-Aug-2007 11:29
18-Aug-2007 11:29
You may asign classes to arrays:
<?php
class foo
{
function test_foo()
{
echo "test_foo 1 2 3<br />";
}
}
class bar
{
function test_bar()
{
echo "test_bar 1 2 3<br />";
}
}
$classes = array();
$classes['foo'] = new foo();
$classes['bar'] = new bar();
$classes['foo']->test_foo();
$classes['bar']->test_bar();
?>
Output:
test_foo 1 2 3
test_bar 1 2 3
chris at simplekiosks dot com
13-Apr-2006 09:31
13-Apr-2006 09:31
I took the above examples and extented them slightly to also allow you to run any function in the subclass without having to first declare it in the main class.
Enjoy
<?php
class mainClass
{
/*
* Class loading function.
*
*
*
*
*/
var $module;
function LoadClass($loadModule)
{
$this->module = new $loadModule; // this is much better
}
function RunFunction($FunctionName)
{
$this->module->$FunctionName();
}
function ListFunctions()
{
}
// function out()
//{
// $this->module->out();
// }
}
class subclass
{
function out()
{
echo "Worked";
}
function NewFunction()
{
echo "<br>Good Lord<br>";
}
function ThirdFunction()
{
echo "<br>eh....<br>";
}
}
echo "Start of class manulapations<br>";
//$loadModule = new subclass;
$mainclass=new mainClass;
$mainclass->LoadClass("subclass");
//$mainclass->out();
$mainclass->RunFunction('NewFunction');
//$mainclass->ThirdFunction();
echo "End of class manulapation<br>";
?>
Leonel Quinteros
09-Feb-2006 06:57
09-Feb-2006 06:57
PHP Allow to extend a class in a dinamic way into a object and only affects that object not the others of the same class.
I was developing a persistence class and i found this:
<?php
class MyClass {
var $Prop1;
// Into the constructor i create a propertie that was not declared before.
function MyClass() {
$this->Prop2 = "This was not declared but now exists into the object";
}
function setProp($PropName, $PropValue) {
$this->$PropName = $PropValue;
}
}
$MyObj = new MyClass();
$MyObj->setProp("Prop1", "This was declared and now has value");
$MyObj->setProp("Prop3", "This was declared by setProp() method.");
$MyObj->Prop4 = "This was declared out of the class definition";
echo "Prop1: ".$MyObj->Prop1." <br />\r\n";
echo "Prop2: ".$MyObj->Prop2." <br />\r\n";
echo "Prop3: ".$MyObj->Prop3." <br />\r\n";
echo "Prop4: ".$MyObj->Prop4." <br />\r\n";
?>
This could be very useful, but very dangerous too, take care.
Wolverine
01-Feb-2006 09:30
01-Feb-2006 09:30
In case you would like to interrupt object construction on some condition and return false for further checking:
<?php
class Foo
{
// Constructor
function Foo()
{
/* Some inits here */
$someval=false;
if ($someval===false)
{
return false;
}
}
}
$obj=new Foo(); // This won't work and will return partially initialised object instead of false
class Bar
{
// Constructor
function Bar()
{
/* Some inits here */
$someval=false;
if ($someval===false)
{
$this=false;
return;
}
}
}
$obj2=new Bar(); // This will work as expected and return false
?>
Hope this helps some people.
Karim Ahmed
20-Oct-2005 12:46
20-Oct-2005 12:46
This class method allows you to take a nice associative array of parameters into your class when the number of parameters gets unmanagable and/or has lots of default-value parameters.
It is so useful I suggest putting on a general base class (I call mine Object) so all your descendents can use it.
-----------------------------------------------------
Code:
-----------------------------------------------------
function setClassVars( &$parameter_array )
{
$class = get_class($this);
$class_vars = get_class_vars($class);
/*
* check that each of the passed parameters are valid before setting the
* appropriate class variable.
*/
foreach ( $parameter_array as $var => $value ){
if ( array_key_exists( $var, $class_vars ) ){
$this->$var = $value;
}
else{
$this->raiseError(
'setClassVars: class variable "' .
$var .
'" does not exist on class "' .
$class . '"'
);
}
}
}
-----------------------------------------------------
for example:
A complicated, messy, class method Before:
-----------------------------------------------------
render(
&$business_object,
$on_change=false,
$on_blur=false,
$options=false
$name
){
$this->business_object = $business_object;
$this->name = $name;
$this->on_blur = $on_blur;
$this->options = $options;
<code>
}
-----------------------------------------------------
A nice clean method After:
-----------------------------------------------------
render(
&$parameter_array
){
$this->setClassVars($parameter_array);
<code>
}
-----------------------------------------------------
Example call:
-----------------------------------------------------
$parameter_array =
array(
'business_object' => $business_object,
'name' => $field_name,
'on_change' => 'form.submit()',
'on_blur' => 'javascript:validate()',
$options =>
array(
'1' => 'None Selected',
'2' => 'Blue',
'3' => 'Red'
)
);
$my_object->render( &$parameters );
-----------------------------------------------------
Now isn't that easier to read AND maintain. Now you can change your API without the hassle of amending every call to the method! You no longer have to worry about where the default params are or even the order of your params.
I hope someone else who has been swearing at their code finds this useful ;-)
Felix M dot Palmen <fmp at palmen dot homeip dot net>
10-Oct-2005 01:18
10-Oct-2005 01:18
My way to implement a singleton in PHP4. I think it's the most convenient one since it works transparently using the constructor. Thanks to S.Radovanovic for his idea with referencing the class' variables, posted on http://www.php.net/manual/en/language.variables.scope.php
<?php
/* Singleton. Every instatiation returns the "same" object.
*
* for this to work, ALWAYS create objects with $object =& new class().
* The reference operator doesn't do any harm in general and is
* necessary for singletons.
*
* You also need to declare all the class' variables with "var" for
* a singleton subclass. But that should always be a rule of good
* design :)
*
* call parent::singleton() first in your subclass constructor.
*
* Of course, the subclass constructor should check if the object is already
* initialized before doing any initialization.
*/
class singleton
{
function singleton()
{
// static associative array containing the real objects, key is classname
static $instances=array();
// get classname
$class = get_class($this);
if (!array_key_exists($class, $instances))
{
// does not yet exist, save in array
$instances[$class] = $this;
}
// PHP doesn't allow us to assign a reference to $this, so we do this
// little trick and fill our new object with references to the original
// class' variables:
foreach (get_class_vars($class) as $var => $value)
{
$this->$var =& $instances[$class]->$var;
}
}
}
?>
dave at davidhbrown dot us
03-Oct-2005 09:10
03-Oct-2005 09:10
It appears that one must use eval if calling a static function where the name of the class is in a variable:
echo $class::staticfunc();
gets you a "parse error, unexpected T_PAAMAYIM_NEKUDOTAYIM" (in PHP 4.4.0)
while
echo eval("return $class::staticfunc();");
behaves as desired.
Contrast this limitation with `->`which will accept a variable on both sides -- e.g., $myClass->$myFunc() -- and, of course, new $myClass is perfectly happy. The expression myClass::$myFunc() also works.
ia [AT] zoznam [DOT] sk
28-Sep-2005 02:45
28-Sep-2005 02:45
to Menno Vanderlist:
And why bother to use eval?
<?php
class mainClass
{ //mainClass
var $module;
function mainClass($loadModule)
{ // load modules
//eval("\$this->module = new $loadModule;");
$this->module = new $loadModule; // this is much better
}
function out()
{ //print out of loaded module
$this->module->out();
}
}
?>
Functionality is the same, without the overhead when using eval().
alberto dot delatorre at gmail dot com
11-Feb-2005 03:11
11-Feb-2005 03:11
If you have a class hierarchy as this:
<?php
abstract class A{
//construct ommited
public function load(){
$this->_load();
}
protected abstract function _load();
}
class B extends A{
protected function _load(){
echo "loaded";
}
}
$b = new B();
$b->load();
?>
you encountered that you will have a 'calling an abstract method' in the line with '$this->_load'. To avoid this, just make another reference to $this and then call the method you'd want, this way:
<?php
abstract class A{
//construct ommited
public function load(){
$aux_this=&$this;
$aux_this->_load();
}
protected abstract function _load();
}
class B extends A{
protected function _load(){
echo "loaded";
}
}
$b = new B();
$b->load();
?>
arjini at gmail dot com
04-Feb-2005 01:56
04-Feb-2005 01:56
Didn't see this anywhere obvious, so I'm posting it here. To access a memeber of an array with another variable you use $arr[$name]
To access a class method or property, you use $obj->{$name} You can also use the return value of a function.
<?php
class Test {
function methodName(){
echo 'works!';
}
}
function getName(){
return 'methodName';
}
$t = new Test();
$t->{getName()}();
//works!
?>
spam at modem-help dot com
23-Jan-2005 09:32
23-Jan-2005 09:32
Although the php 4.2.2 parser and variable storage are case-sensitive, classes + class-function + function declaration *storage* are not.
To example this, consider the following:
[note: constructor is `sendfile()', not `SendFile()' nor `sendFile()']
<?php
class SendFile {
// variables declared here
function SendFile() {
// function defined here
}
function sendFile() {
// function defined here
}
function sendfile() {
// function defined here
}
} // end class SendFile
?>
This was eventually illuminated by:
<?php
print_r( get_declared_classes());
?>
...in which a snippet of the result is:
Array
(
[0] => stdClass
[1] => __PHP_Incomplete_Class
[2] => Directory
[3] => DomNode
[4] => DomDocument
[5] => DomParser
...
[24] => sendfile
)
Specifically, it appears that php has used initial-caps for all of it`s own (internal) classes, but that all user-classes are stored lower-cased, as are class + ordinary functions.
Written in the hope of saving someone else time & grief from this interesting `feature'.
rdc_uk
22-Jan-2005 08:44
22-Jan-2005 08:44
Just found this interesting "gotcha";
If you implement a class with no member variables, calling the constructor does NOT produce an object. This can be a source of (great) consternation when producing classes which need no data storage.
Essentially if your class has no data members, all its methods are ONLY available statically, this can be a pain if defining object hierarchies with abstract base classes...
Example:
class A
{
function A()
{
$i = 0; // not an empty constructor!
}
function fn()
{
return "A";
}
}
$obj_a = new A();
$obj_a == null
$obj_a->fn(); will generate an error
A::fn(); works
Simply putting a "var $status=0;" in the class suddenly makes your object instantiatable.
This is certainly a "quirk" in an OO implementation, possibly a bug, definitely worth watching out for...
php dot net at mechintosh dot com
05-Dec-2004 03:52
05-Dec-2004 03:52
While it is possible to use the names of existing PHP functions for class method names (not that you *should*, however sometimes there's really only one good name for a method even if it's taken..), you cannot use the names of language constructs like list(), echo, print etc, and appearantly also not of eval().
But you probably shouldn't be using PHP functionnames anyway :-)
email at richardlee dot info
05-Sep-2004 10:11
05-Sep-2004 10:11
An example of how to pass an object back into its own class for direct use.
(thisClass.php)
<?php
class thisClass{
var $var1;
function thisClass($value)
{$this->var1 = $value;}
function set_var1($value)
{$this->var1 = $value;}
function get_var1()
{return $this->var1;}
function showVar()
{echo "<p>var1 = ".$this->var1."</p>";}
function callShowVar($object)
{$object->showVar();}
function copyObject($object)
{$this->var1 = $object->get_var1();}
}
?>
(test.php)
<?php
require_once('class.php');
$thisObject = new thisClass(3);
$thatObject = new thisClass(1);
$thatObject->callShowVar($thisObject); //outputs "var1 = 3"
$thisObject->showVar(); //outputs "var1 = 3"
$thatObject->showVar(); //outputs "var1 = 1"
$thatObject->copyObject($thisObject);
$thatObject->showVar(); //outputs "var1 = 3"
?>
babs at sntteam dot org
31-Aug-2004 07:22
31-Aug-2004 07:22
We can't split the class declaration in multiple PHP section but we can exit php tag in a function . ex :
<?
class plop {
function plop() {
$this->whatever = "bar";
}
function foo() {
?>
<pre>foo returns <?=$this->whatever?></pre>
<?
}
};
$a = new plop;
$a->foo();
?>
will print : foo returns bar
PHP Version 4.3.8-9
bishop
19-Jul-2004 06:04
19-Jul-2004 06:04
Say you have a factory method that needs to put data into an object before the constructor is called. This might be necessary, for example, if the factory class establishes a connection to a database and the manufactured object uses that connection in the constructor.
Do something like this:
<?php
function &factory($class /* ... */) {
// 1) get an object shell
$obj = new stdClass();
// 2) "type cast" it to the desired class
$tmp = explode(':', serialize($obj));
$tmp[1] = strlen($class);
$tmp[2] = '"' . $class . '"';
$obj = unserialize(implode(':', $tmp));
// 3) copy construct the manufacturer into the manufacturee
$obj->copyFrom($this);
// 4) call the real constructor
$args = func_get_args();
array_shift($args); // skip the class
call_user_func_array(array (&$obj, $class), $args);
return $obj;
}
?>
NOTE: The Editor's note in the "simon dot li at hongkong dot com" entry is misleading; it only works because the class names "foo" and "bar" are the same length. In general, you must change the first and second entries in serialized array as done above.
Also NOTE: This typecasting business works if you have a function that takes an arbitrary number of arguments and you want to pass those arbitrary arguments into a constructed class. You can't just use call_user_func_array() in that case because 'new' is an operator, not a function.
catalin dot ivan at utoronto dot ca
06-Jul-2004 03:50
06-Jul-2004 03:50
Regarding defining class variables:
The 'var' statement can NOT take Heredoc definitions, i.e. the "<<<MARKER" stuff (these may be somehow 'dynamic' as per warning above).
You must assign them values within the class constructor if you must use Heredoc.
oran at anonimous dot biu dot ac dot il
16-Jun-2003 10:34
16-Jun-2003 10:34
class baseclass {
function static1() {return "bla";}
function static2() {return call_user_func(array(__CLASS__,'static1'));}
}
[ Editor's Note: Using the above, rather than below, will allow the static function to call its own generation's version of the method. ]
Unfortunately, inheritance of static methods is a bit problematic in PHP, because in order to use a static method you have to know the exact class it's defined in. This means trouble if you want to use one static function (or a static variable) from within another static function. For example:
class baseclass {
function static1() {return "bla";}
function static2() {return baseclass::static1();}
}
Now suppose that you write a class newclass that extends baseclass and redefines static1() to return "foo" instead of "bla" - this change will not be reflected in static2() of newclass. Not good at all.
You could use $this->static1() instead of baseclass::static1() in the definition of static2(), but then static2() will not be a static method. Another idea is to use get_class_name() to get the class name inside static2(), but again you need the $this variable to make this function call.
I found no way to overcome this problem, except to use real functions (not methods) for the purpose of wrapping my static functions. The name of the exact class to use is passed as a parameter to the wrapping function. It looks like this:
function wrapped_static1($clname) {
if (in_array('static1', get_class_methods($clname)))
return $clname::static1();
return baseclass::static1();
}
function wrapped_static2($clname) {
if (in_array('static2', get_class_methods($clname)))
return $clname::static2();
return baseclass::static2();
}
class baseclass {
function static1() {return "bla";}
function static2() {return wrapped_static1('baseclass');}
}
Now you can go on using baseclass and writing extension classes for it, using the following rules:
1. Use inheritance with your static functions in the natural way, as you would in C++. The wrapping code given here supports just 1 level of inheritance, but it may be improved to work its way up the inheritance tree using PHP's class functions.
2. When calling a static function, always call it through its wrapper.
For example:
class newclass extends baseclass // example for rule 1
{
function static1() {return 'foo';}
}
print static2_wrapper('newclass'); // example for rule 2
This is a little cumbersome, but now when you redefine a static function, you can be sure that any functions that rely on it will be able to use the correct definition.
russ dot taylor at nifty dot com
18-Apr-2003 01:31
18-Apr-2003 01:31
It is sometimes useful to register a class instance as a session variable. This can allow classes and their contained values to persist across multiple pages and/or frames. Frames which need to use the registered class must be loaded (or reloaded) after the class instance is registered and the class declaration must be included in each file that needs to access the registered class.
i.e.
<?
session_start();// must have a session, duh...
class foo{//normal class declaration
var $bar;
function foo(){//normal constructor
$this->bar = "a value to share and persist";
}
}
$vital = new foo;//instance "vital" of object type "foo"
session_register("vital");//register the instance "vital"
//other code as needed
?>
**NOTE: it would be helpful to include the class from an external source so the same declaration could be used everywhere its needed, duh
then simply include the class declaration in any other file and you will have access to the registered class instance. in a separate frame on the same page you could use ...
<?
session_start();
class foo{//same class declaration
var $bar;
function foo(){//normal constructor
$this->bar = "a value to share and persist";
}
}
echo $vital->bar;
?>
**NOTE: if you use a frameset you must allow processing time of the session registration or the value will not be available! You can use any number of methods to trigger the delay, but the session must NOT be started on the second page beforre the variable is registered on the first. On option is to use an onload statement in the first frames body tag, assuming normal html output...
<html><head></head><body onLoad="parent.frame[1].location.reload();"><!--what ever else you need to output--></body></html>
"frame[1]" assumes a two frame layout with frame[0] containing the values to share and frame[1] requiring those values. thus this, when included in frame[0] will force a reload of frame[1] AFTER the class instance was registered.
mcoakley at netplay dot net
17-Jan-2003 08:47
17-Jan-2003 08:47
In response to the comments above and using tomcats example directly... I love scripting languages and I love PHP the most out of them. While most programmers (and editors notes) try to state that PHP is not a true OO language it has what you need to develop good OO programs. Sure some of the really strong structured things aren't there but that is the fun you get with scripted languages. But after reading every comment on this page I think people (and I know I am going to get flamed for this one...) should start to fully understand the principles of OO programming: Encapsulation, Polymorphism and Abstraction.
For those new to those terms:
- Encapsulation is what you get when you can have data and the methods that act on those data in an "encapsulated" entity (object)
- Polymorphism is a property of objects that comes through inheritence that allows methods of the same name to perform different (but similar in purpose) actions
- Abstration provides a mechanism to design effective OO heirarchies by pulling common methods or actions into superclasses and using inheritence to provide functionality
If these principles are understood fully, PHP can be used as a great OO language. Another common complaint is that PHP doesn't offer private/protected members/methods, I too would like to see these features. One BIG thing to keep in mind while desiging an OO program is that the objects should provide funtionality at the class level. Don't think of objects as individual entities but think of a heirarchy that provides "blackboxes" of code. In otherwords the class names should tell you what the object does and the methods only tell you how to invoke the functionality. You should never be concerned with how the object achieves its functionality.
b dot ruecker at portunity dot de
08-Jul-2001 09:22
08-Jul-2001 09:22
If you need a destructor, perhaps it is an idear to simulate it this way with a global Destroy-Function:
<?
function DestroyObject ($name)
{
$theobject = &$GLOBALS[$name];
if (method_exists ($theobject,"Destroy"))
$theobject->Destroy ();
unset ($GLOBALS[$name]);
}
class xyz
{
var $somevar;
// ### This is the constructor
function xyz ()
{
}
// ### This is the destructor which will be called
function Destroy ()
{
echo ("Now we destroy it !");
}
function SomeDo ()
{
echo ("doing something: ".$this->somevar);
}
}
$example = new xyz;
// .... doing something here
$example->somevar = 3;
$example->SomeDo();
DestroyObject ("example");
// ### Test => should produce an error !
$example->SomeDo ();
?>
sgarner at expio dot co dot nz
18-Feb-2001 06:15
18-Feb-2001 06:15
[Editor's note: Remember tha PHP is not a hard core OOP language, and even the ones that are do not always support the unusual vector/array references applied to results from methods.]
It seems there is no way to access the return value of a method (or any function) inline, without assigning it to a variable.
For example:
<?php
class Test
{
function blah ()
{
return array(1,2,3);
}
function childTest ()
{
return new Test;
}
}
$test = new Test;
// This does not work:
$foo = $test->blah()[0];
// Instead have to do:
$temp = $test->blah();
$foo = $temp[0];
// Similarly for objects, cannot do:
$foo = $test->childTest()->blah();
// Instead have to do:
$temp = $test->childTest();
$foo = $temp->blah();
?>
buzz77 at gmx dot net
14-Feb-2001 08:33
14-Feb-2001 08:33
You can also store object variables as session variables, so that you don't have to create an object every time the page loads.
Let's see how:
here is my simple class file:
// simple.lib.php
class simple
{
function dummy
{
print "TEST SUCCESSFUL!\n";
}
}
Then, I create a simple .php which starts a new session and registers the object-variable of the "simple"-class.
// test1.php
require ("simple.lib.php");
session_start();
session_register("CLASSOBJ");
$CLASSOBJ=new simple();
That's all.
In the following .php-files you've only to add the following lines:
require("simple.lib.php");
session_start();
To test out if it works, simply call:
$CLASSOBJ->dummy();
and it will print the message.
I tried it out also with quite huge classes, and it always worked (I think the pointer to the instanciated class is stored and the class object itself won't be deleted if you eg. change to another .php-page)
brice at webprojkt dot com
21-Dec-2000 09:23
21-Dec-2000 09:23
Defaulting a function parameter to a variable isn't directly supported, but here's how to get around that:
Suppose you have a class:
class query {
var $sql;
var $link;
function go ($SQLstring = $this->sql)
{
return mysql_query($this->sql,$link);
}
}
This doesn't work. Here's the workaround:
(function spec):
function go ($SQLstring)
{
if (isset($SQLstring)) { $this->sql = $SQLstring; }
return mysql_query($this->sql,$this->link);
}
This may not be the best example of this, but I thought I'd throw this out for you folks ... should allow support of presetting of an object value and then execution of the method on that, or something like query::go("SELECT ...");
Enjoy!
p.s. (in this case query::go wouldn't work because it is coded with $this->link, but if you wanted to just use the default connection, it'd work fine :)
iw at warped dot nu
08-Oct-2000 05:12
08-Oct-2000 05:12
Here's a very important reminder to those of you used to Java/C++ object references/pointers. When you send a function arguments which include a class object, PHP will make copies of that object for use inside that function.
This differs from passing a Java reference to an object or passing a C++ pointer to an object. Within the scope of the above-mentioned function, calling class methods of the argument object will only affect the copy that PHP creates. Likewise, when the function itself is completed, the copy of the object you passed ceases to exist.
To emulate Java/C++ functionality of arguments that are objects, you just have to modify the given function's signature from this:
function foo(..., $object, ...)
to this:
function foo(..., &$object, ...)
The ampersand(&) thus signifies that the function should receive a reference to the object, instead of creating a copy of the object.
simon dot li at hongkong dot com
13-Sep-2000 04:15
13-Sep-2000 04:15
-------------------------------------------------
[Editor's note: class casting per se is not part of the object/class implementation in PHP, but code like the one in this note can kludge if you need it for very simple cases, more complex ones are left to the imagination of the programmer:
<?php
class foo {
function foo($name="foo") {
$this->name=$name;
}
}
class bar extends foo {
function boom() {
echo "BOOOM!";
}
}
$f = new foo();
$temp = explode(":",serialize($f));
$temp[2] = "\"bar\"";
$b = unserialize(implode(":",$temp));
$b->boom();
?>
This forces $b to be an instance of "bar" using an object $f, an instance of "foo"]
-------------------------------------------------
About casting of object, say, i got:
class A extends B {
function A() {
$this->B();
}
....
}
$b = new B();
$a = new A();
I wanna have a object of class A with "content" of $b:
$a = (A) $b; // not a valid code,(right?) as for illustration.