crypt
hemanman at gmail dot com, the problem is that func() doesn't actually return a value (string or otherwise), so the result of echoing func() is null.
With the comma version, each argument is evaluated and echoed in turn: first the literal string (simple), then func(). Evaluating a function call obviously calls the function (and in this case executes its own internal echo), and the result (null) is then echoed accordingly. So we end up with "outside func() within func()" as we would expect.
Thus:
<?
echo "outside func ()\n", func ();
?>
effectively becomes:
<?
echo "outside func ()\n";
//func ()
{
echo "within func ()\n";
}
echo '';
?>
The dot version is different: there's only one argument here, and it has to be fully evaluated before it can be echoed as requested. So we start at the beginning again: a literal string, no problem, then a concatenator, then a function call. Obviously the function call has to be evaluated before the result can be concatenated with the literal string, and THAT has to happen BEFORE we can complete the echo command. But evaluating func() produces its own call to echo, which promptly gets executed.
Thus:
<?
echo "outside func ()\n" . func ();
?>
effectively becomes:
<?
//func ()
{
echo "within func ()\n";
}
echo "outside func ()\n" . '';
?>
echo
(PHP 4, PHP 5)
echo — Εμφανίστε ένα ή περισσότερα strings
Περιγραφή
void echo
( string $arg1
[, string $argn...
] )
Εμφανίζει όλες τις παραμέτρους.
Η echo() δεν είναι στην πραγματικότητα μία συνάρτηση (είναι ένα γλωσσικό κατασκεύασμα) κι έτσι δεν είστε αναγκασμένοι να χρησιμοποιείται παρενθέσεις με αυτήν. Στην πραγματικότητα, εάν θέλετε να περάσετε πάνω από ένα όρισμα στην echo, δεν πρέπει να περικλείσετε τις παραμέτρους σε παρενθέσεις.
Example#1 Παραδείγματα χρήσης της echo()
<?php
echo "Hello World";
echo "This spans
multiple lines. The newlines will be
output as well";
echo "This spans\nmultiple lines. The newlines will be\noutput as well.";
echo "Escaping characters is done \"Like this\".";
// You can use variables inside of an echo statement
$foo = "foobar";
$bar = "barbaz";
echo "foo is $foo"; // foo is foobar
// You can also use arrays
$bar = array("value" => "foo");
echo "this is {$bar['value']} !"; // this is foo !
// Using single quotes will print the variable name, not the value
echo 'foo is $foo'; // foo is $foo
// If you are not using any other characters, you can just echo variables
echo $foo; // foobar
echo $foo,$bar; // foobarbarbaz
echo <<<END
This uses the "here document" syntax to output
multiple lines with $variable interpolation. Note
that the here document terminator must appear on a
line with just a semicolon no extra whitespace!
END;
// Because echo is not a function, following code is invalid.
($some_var) ? echo('true'): echo('false');
// However, the following examples will work:
($some_var) ? print('true'): print('false'); // print is a function
echo $some_var ? 'true': 'false'; // changing the statement around
?>
Η συνάρτηση echo() έχει μία πιο σύντομη σύνταξη, όπου το tag ανοίγματος μπορεί να ακολουθείται, αμέσως, από ένα ίσον. Η σύνταξη αυτή λειτουργεί μόνο εάν η ρύθμιση short_open_tag του configuration έχει τεθεί σε λειτουργία.
I have <?=$foo?> foo.
Για περισσότερο προβληματισμό αναφορικά με τις διαφορές μεταξύ των συναρτήσεων print() και echo(), διαβάστε αυτό το FAQTs Knowledge Base Article: » http://www.faqts.com/knowledge_base/view.phtml/aid/1/fid/40
Note: Επειδή αυτό είναι μια δομή της γλώσσας και όχι μια συνάρτηση, δεν μπορεί να καλεστεί χρησιμοποιώντας συναρτήσεις μεταβλητών
add a note
User Contributed Notesecho
nikolaas dot mennega at links dot com dot au
01-Nov-2007 12:04
01-Nov-2007 12:04
Jason Carlson - SiteSanity
16-May-2005 10:28
16-May-2005 10:28
In response to Ryan's post with his echobig() function, using str_split wastes memory resources for what you are doing.
If all you want to do is echo smaller chunks of a large string, I found the following code to perform better and it will work in PHP versions 3+
<?php
function echobig($string, $bufferSize = 8192)
{
// suggest doing a test for Integer & positive bufferSize
for ($chars=strlen($string)-1,$start=0;$start <= $chars;$start += $bufferSize) {
echo substr($string,$start,$buffer_size);
}
}
?>
ryan at wonko dot com
27-Feb-2005 12:56
27-Feb-2005 12:56
Due to the way TCP/IP packets are buffered, using echo to send large strings to the client may cause a severe performance hit. Sometimes it can add as much as an entire second to the processing time of the script. This even happens when output buffering is used.
If you need to echo a large string, break it into smaller chunks first and then echo each chunk. The following function will do the trick in PHP5:
<?php
function echobig($string, $bufferSize = 8192)
{
$splitString = str_split($string, $bufferSize);
foreach($splitString as $chunk)
echo $chunk;
}
?>
zombie)at(localm)dot(org)
25-Jan-2003 11:26
25-Jan-2003 11:26
[Ed. Note: During normal execution, the buffer (where echo's arguments go) is not flushed (sent) after each write to the buffer. To do that you'd need to use the flush() function, and even that may not cause the data to be sent, depending on your web server.]
Echo is an i/o process and i/o processes are typically time consuming. For the longest time i have been outputting content by echoing as i get the data to output. Therefore i might have hundreds of echoes in my document. Recently, i have switched to concatenating all my string output together and then just doing one echo at the end. This organizes the code more, and i do believe cuts down on a bit of time. Likewise, i benchmark all my pages and echo seems to influence this as well. At the top of the page i get the micro time, and at the end i figure out how long the page took to process. With the old method of "echo as you go" the processing time seemed to be dependent on the user's net connection as well as the servers processing speed. This was probably due to how echo works and the sending of packets of info back and forth to the user. One an one script i was getting .0004 secs on a cable modem, and a friend of mine in on dialup was getting .2 secs. Finally, to test that echo is slow; I built strings of XML and XSLT and used the PHP sablotron functions to do a transformation and return a new string. I then echoed the string. Before the echo, the process time was around .025 seconds and .4 after the echo. So if you are big into getting the actual processing time of your scripts, don't include echoes since they seem to be user dependent. Note that this is just my experience and it could be a fluke.