ob_start();
header("Content-Length: " . filesize ( $fullUrl ) );
header("Content-type: application/octet-stream");
header("Content-disposition: attachment; filename=".basename($fullUrl));
header('Expires: 0');
header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
ob_clean();
flush();
readfile($fullUrl);