private static function cache($mtime) {
		$gmt_mtime = gmdate('D, d M Y H:i:s', $mtime).' GMT';

		header('Cache-Control: public');
		header('Pragma: public');

		if(isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
			if ($_SERVER['HTTP_IF_MODIFIED_SINCE'] == $gmt_mtime) {
				header('Expires: ');
				HTTP\Status::code_304();
			}
		}

		header('Last-Modified: '. $gmt_mtime);
		header('Expires: '.gmdate('D, d M Y H:i:s', strtotime('+30 minutes')).' GMT');
	}