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 — Visualizza una o più stringhe
Descrizione
void echo
( string $arg1
[, string $...
] )
Visualizza tutti i parametri.
echo() in realtà non è una funzione (è un costrutto del linguaggio) pertanto non richiede l'uso di parametri. Infatti, se si vuole passare più di un parametro, non bisogna racchiuderli tra parentesi.
Example #1 Esempi di uso di 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\".";
// Si possono utilizzare variabili all'interno dei parametri di echo
$foo = "foobar";
$bar = "barbaz";
echo "foo is $foo"; // foo is foobar
// Si possono utilizzare anche delle matrici
$bar = array("value" => "foo");
echo "this is {$bar['value']} !"; // this is foo !
// Utilizzando gli apici singoli viene visualizzato il nome della variabile, non il valore
echo 'foo is $foo'; // foo is $foo
// Se non vi sono altri caratteri, si può visualizzare soltanto il contenuto delle variabili
echo $foo; // foobar
echo $foo,$bar; // foobarbarbaz
// Alcuni programmatori preferiscono passare i parametri come sequenza di stringhe concatenate.
echo 'This ', 'string ', 'was ', 'made ', 'with multiple parameters.', chr(10);
echo 'This ' . 'string ' . 'was ' . 'made ' . 'with concatenation.' . "\n";
echo <<<END
Questo esempio utilizza la sintassi "here document"
per visualizzare più linee oltre al contenuto di $variable
Notare che il terminatore del testo richiede
anche il punto e virgola, senza alcun spazio aggiuntivo!
END;
// Poichè echo non è una funzione la seguente riga non è valida.
($some_var) ? echo 'true' : echo 'false';
// Tuttavia la seguente funziona
($some_var) ? print('true'): print('false'); // print è una funzione
echo $some_var ? 'true': 'false'; // altra versione dell'istruzione
?>
echo() ha una sintassi alternativa abbreviata in cui si può fare seguire alle tag di apertura il segno di uguale. Questa sintassi abbreviata funziona solo se il parametro di configurazione short_open_tag è abilitato.
I have <?=$foo?> foo.
Per una breve discussione sulle differenze tra print() e echo(), vedere FAQTs Knowledge Base Article: » http://www.faqts.com/knowledge_base/view.phtml/aid/1/fid/40
Nota: Poichè questo è un costrutto del linguaggio e non una funzione, non può essere chiamato con le variabili funzione
add a note
User Contributed Notesecho
nikolaas dot mennega at links dot com dot au
01-Nov-2007 09:04
01-Nov-2007 09:04
Jason Carlson - SiteSanity
16-May-2005 08:28
16-May-2005 08:28
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 10:56
27-Feb-2005 10:56
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 09:26
25-Jan-2003 09:26
[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.