Is there a way to get the current HTTP response code with PHP?

Is there a way to get the HTTP response code to be sent from a PHP script, for example a script like this:

header('HTTP/1.1 404 Not Found');

$code = imaginary-function(); // $code contains 404

I noticed a function http_response_codein PHP docs, but this doesn't seem to be available in PHP 5.3.9.

Thanks in advance!