Status Code 304 manipulation for PHP. Allows a dynamically controlled "Last Modified" header for dynamic content, thus allowing for performance.

gistfile1.aw

<?php
$_HEADERS = apache_request_headers(); # Get client headers.
$updateTime = strtotime('yesterday'); # Makes sure that it always caches.

/*
Mock page content.
Change this after first view. If refreshing
shows the old content, then the test worked!
*/

$content = 'test!';

if(isset($_HEADERS['If-Modified-Since']) && (strtotime($_HEADERS['If-Modified-Since']) == $updateTime)) {
	// Unmodified!
	header('Last-Modified: '.gmdate('D, d M Y H:i:s', $updateTime).' GMT', true, 304);
	exit;
} else {
	// Modified or unsupported!
	header('Last-Modified: '.gmdate('D, d M Y H:i:s', $updateTime).' GMT', true, 200);
	echo $content;
}