header_register_callback

(No version information available, might only be in Git)

header_register_callbackCall a header function

Description

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.

Parameters

callback

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

Return Values

Returns TRUE on success or FALSE on failure.

Examples

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";
?>

The above example will output something similar to:

Content-Type: text/plain

a

Notes

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

Note:

Headers will only be accessible and output when a SAPI that supports them is in use.

See Also

add a note add a note

User Contributed Notes 1 note

up
2
matt@kafene
1 year 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
To Top