download header file

[84morena]

raga con questo script riesco ad effettuare il download per qualsiasi file...escluso zip!!!
qualcuno ha mai effettuato download di file zip?

$file=$_REQUEST["nome_file"];
    $cartella = $_SERVER["DOCUMENT_ROOT"].CARTELLA_SOFTWARE."/materiale/";
    $percorso_file=$cartella.$file;
    $dimensione_file=filesize($percorso_file);

    $len = filesize($percorso_file);
    $filename = basename($file);
    $file_extension = strtolower(substr(strrchr($filename,"."),1));


    switch( $file_extension ) {
          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 "jpeg":
      case "jpg": $ctype="image/jpg"; break;
      case "mp3": $ctype="audio/mpeg"; break;
      case "wav": $ctype="audio/x-wav"; break;
      case "mpeg":
      case "mpg":
      case "mpe": $ctype="video/mpeg"; break;
      case "mov": $ctype="video/quicktime"; break;
      case "avi": $ctype="video/x-msvideo"; break;

      case "php":
      case "htm":
      case "html":
      case "txt": $ctype="text/txt"; break;

      default: $ctype="application/force-download";
    }

    ob_end_clean();
    
    header("Pragma: public");
    header("Expires: 0");
    header("Cache-Control: must-revalidate, post-check=0, pre-check=0");
    header("Cache-Control: public");
    header("Content-Description: File Transfer");
   

    header("Content-Type: $ctype");

    $header="Content-Disposition: attachment; filename=".$filename.";";
    header($header );
    header("Content-Transfer-Encoding: binary");
    header("Content-Length: ".$len);
    @readfile($dir.$file);
    exit;