header_register_callback

(PHP 5 >= 5.4.0, PHP 7)

Call a header function

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.

Returns:

Returns TRUE on success or FALSE on failure.

Notes:

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

Examples:

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