php man page for headers_list

HEADERS_LIST(3) 							 1							   HEADERS_LIST(3)

headers_list - Returns a list of response headers sent (or ready to send)

SYNOPSIS
       array headers_list (void  )

DESCRIPTION
       headers_list(3)	will return a list of headers to be sent to the browser / client. To determine whether or not these headers have been sent
       yet, use headers_sent(3).

RETURN VALUES
	Returns a numerically indexed array of headers.

EXAMPLES
       Example #1

	      Examples using headers_list(3)

	      <?php

	      /* setcookie() will add a response header on its own */
	      setcookie('foo', 'bar');

	      /* Define a custom response header
		 This will be ignored by most clients */
	      header("X-Sample-Test: foo");

	      /* Specify plain text content in our response */
	      header('Content-type: text/plain');

	      /* What headers are going to be sent? */
	      var_dump(headers_list());

	      ?>

	      The above example will output:

	      array(4) {
		[0]=>
		string(23) "X-Powered-By: PHP/5.1.3"
		[1]=>
		string(19) "Set-Cookie: foo=bar"
		[2]=>
		string(18) "X-Sample-Test: foo"
		[3]=>
		string(24) "Content-type: text/plain"
	      }

NOTES
       Note

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

SEE ALSO
       headers_sent(3), header(3), setcookie(3), apache_response_headers(3), http_response_code(3).

PHP Documentation Group 													   HEADERS_LIST(3)