header_register_callback(3) [php man page]

HEADER_REGISTER_CALLBACK(3)						 1					       HEADER_REGISTER_CALLBACK(3)

header_register_callback - Call a header function

SYNOPSIS

       bool header_register_callback (callable	$callback)

DESCRIPTION

	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 manip-
       ulate the outgoing headers before being sent.

PARAMETERS

	      o $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(3) 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(3) 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 
headers_list(3), header_remove(3), header(3).
PHP Documentation Group 											       HEADER_REGISTER_CALLBACK(3)