if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
header('HTTP/1.1 304 Not Modified');
header("Last-Modified: " . gmdate("D, d M Y H:i:s", time()) . " GMT");
if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
header('HTTP/1.1 304 Not Modified');
header("Last-Modified: " . gmdate("D, d M Y H:i:s", time()) . " GMT");