header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
header("Expires: Thu, 22 Jan 1987 15:30:00 GMT");
header("Pragma: no-cache");
header("Cache-Control: no-cache, must-revalidate");
header("Cache-Control: post-check=0,pre-check=0", false);
header("Cache-Control: max-age=0", false);