PHP code to implement file downloading in IE

if( empty($_GET['FileName'])|| empty($_GET['FileDir'])|| empty($_GET['FileId'])){
echo' <script> alert("Illegal connection!"); location.replace ("index.php") </script>'; exit();
}
$file_name=$_GET['FileName'];
$ file_dir=$_GET['FileDir'];
$FileId=$_GET['FileId'];
$file_dir = $file_dir."/";
if (!file_exists($file_dir.$file_name)) { //Check Whether the file exists
echo "File not found";
exit;
} else {
$file = fopen($file_dir . $file_name,"r"); // Open the file
// Enter the file label
Header(" Content-type: application/octet-stream");
Header("Accept-Ranges: bytes");
Header("Accept-Length: ".filesize($file_dir . $file_name));
Header("Content- Disposition: attachment; filename=" . $file_name);
// Output file content
echo fread($file,filesize($file_dir . $file_name));
fclose($file);
exit();
}
 ?>