Download File ชื่อภาษาไทย ไม่ได้บน Server 2008 R2 64bit

session_start();
ob_start();

$filename = urldecode($_REQUEST['action']);
$filename = realpath($filename);
$file_extension = strtolower(substr(strrchr($filename,"."),1));
switch ($file_extension) {
case "txt": $ctype="application/txt"; break;
case "pdf": $ctype="application/pdf"; break;
case "exe": $ctype="application/octet-stream"; break;
case "zip": $ctype="application/zip"; break;
case "doc": $ctype="application/msword"; break;
case "xls": $ctype="application/vnd.ms-excel"; break;
case "ppt": $ctype="application/vnd.ms-powerpoint"; break;
case "gif": $ctype="image/gif"; break;
case "png": $ctype="image/png"; break;
case "jpe": case "jpeg":
case "jpg": $ctype="image/jpg"; break;
default: $ctype="application/force-download";
}
if (!file_exists($filename)) {
die("NO FILE HERE");
}
header("Pragma: public");
header("Expires: 0");
header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
header("Cache-Control: private",false);
header("Content-Type: ".$ctype."");
header('Content-Description: File Transfer');
header("Content-Disposition: attachment; filename=".basename($filename).";");
header("Content-Transfer-Encoding: binary");
header("Content-Length: ".filesize($filename));
readfile("".$filename."") or die("File not found.");
ob_clean();