header_register_callback

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header_register_callback — Call a header function

Descrizione

bool header_register_callback ( callable $callback )

Registers a function that will be called when PHP starts sending output.

The callback is executed just after PHP prepares all headers to be sent, and before any other output is sent, creating a window to manipulate the outgoing headers before being sent.

Elenco dei parametri

callback: Function called just before the headers are sent. It gets no parameters and the return value is ignored.

Valori restituiti

Restituisce TRUE in caso di successo, FALSE in caso di fallimento.

Esempi

Example #1 header_register_callback() example


<?php

header('Content-Type: text/plain');
header('X-Test: foo');

function foo() {
 foreach (headers_list() as $header) {
   if (strpos($header, 'X-Powered-By:') !== false) {
     header_remove('X-Powered-By');
   }
   header_remove('X-Test');
 }
}

$result = header_register_callback('foo');
echo "a";
?>

Il precedente esempio visualizzerà qualcosa simile a:

Content-Type: text/plain

a

Note

header_register_callback() is executed just as the headers are about to be sent out, so any output from this function can break output.

Nota:
Gli header sono accessibili (e emessi nell'output) quando è in uso un SAPI che li supporta.

Vedere anche:

headers_list() - Returns a list of response headers sent (or ready to send)
header_remove() - Remove previously set headers
header() - Send a raw HTTP header

add a note User Contributed Notes header_register_callback - [1 notes]

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matt@kafene ¶

2 months ago


Note that this function only registers a single callback as of php 5.4. The most recent callback set is the one that will be executed, they will not be executed in order like with register_shutdown_function(), just overwritten.



Here is my test:



<?php



$i = $j = 0;

header_register_callback(function() use(&$i){ $i+=2; });

header_register_callback(function() use(&$i){ $i+=3; });

register_shutdown_function(function() use(&$j){ $j+=2; });

register_shutdown_function(function() use(&$j){ $j+=3; });

register_shutdown_function(function() use(&$j){ var_dump($j); });

while(!headers_sent()) { echo "<!-- ... flushing ... -->"; }

var_dump(headers_sent(), $i);

exit;



?>



Results:



headers_sent() - true

$i = 3

$j = 5

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