codice:
$input_file = "test.zip";
$download_size = filesize($input_file);
$filename = basename($input_file);
if(ereg("MSIE ([0-9].[0-9]{1,2})", $_SERVER["HTTP_USER_AGENT"])) {
	header("Content-Type: application/octetstream");
	header("Content-Disposition: inline; filename=$filename");
	header("Expires: 0");
	header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
	header("Pragma: public");
	header("Content-Length: $download_size");
} else {
	header("Content-Type: application/octet-stream");
	header("Content-Disposition: attachment; filename=$filename");
	header("Expires: 0");
	header("Pragma: no-cache");
	header("Content-Length: $download_size");
}
readfile($input_file);