PHP - Php Downloading Remote File

Hello everyone.
I have a problem with some of my php script.

I have some php code that downloads a remote file and directly outputs it to the user. It works and all, it's just that when I do it on my Ubuntu LAMP server, downloading a file takes up a lot of ram. On my Windows WAMP server it works correctly and doesn't use up so much ram. Is this a problem with my code, or is it a server configuration?

Below is the code I use to download the file.
Code: [Select]

public function output_file($file, $name, $mime_type='', $size)
   {
   session_write_close();
    /*
    This function takes a path to a file to output ($file),
    the filename that the browser will see ($name) and
    the MIME type of the file ($mime_type, optional).
   
    If you want to do something on download abort/finish,
    register_shutdown_function('function_name');
    */
    if(is_readable($file)) die('File not found or inaccessible!');
    /*
    $size = $size;
    $name = rawurldecode($name); */
   
    /* Figure out the MIME type (if not specified) */
    $known_mime_types=array(
      "pdf" => "application/pdf",
      "txt" => "text/plain",
      "html" => "text/html",
      "htm" => "text/html",
      "exe" => "application/octet-stream",
      "zip" => "application/zip",
      "doc" => "application/msword",
      "xls" => "application/vnd.ms-excel",
      "ppt" => "application/vnd.ms-powerpoint",
      "gif" => "image/gif",
      "png" => "image/png",
      "jpeg"=> "image/jpg",
      "jpg" =>  "image/jpg",
      "php" => "text/plain"
    );
   
    if($mime_type==''){
       $file_extension = strtolower(substr(strrchr($file,"."),1));
       if(array_key_exists($file_extension, $known_mime_types)){
         $mime_type=$known_mime_types[$file_extension];
       } else {
         $mime_type="application/x-rar-compressed";
       };
    };
   
    @ob_end_clean(); //turn off output buffering to decrease cpu usage
   
    // required for IE, otherwise Content-Disposition may be ignored
    if(ini_get('zlib.output_compression'))
     ini_set('zlib.output_compression', 'Off');
   
    header('Content-Type: ' . $mime_type);
    header('Content-Disposition: attachment; filename="'.$name.'"');
    header("Content-Transfer-Encoding: binary");
    header('Accept-Ranges: bytes');
   
    /* The three lines below basically make the
      download non-cacheable */
    header("Cache-control: no-cache");
    //header('Pragma: private');
   // header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
   
    // multipart-download and download resuming support
    if(isset($_SERVER['HTTP_RANGE']))
    {
      list($a, $range) = explode("=",$_SERVER['HTTP_RANGE'],2);
      list($range) = explode(",",$range,2);
      list($range, $range_end) = explode("-", $range);
      $range=intval($range);
      if(!$range_end) {
         $range_end=$size-1;
      } else {
         $range_end=intval($range_end);
      }
   
      $new_length = $range_end-$range+1;
      header("HTTP/1.1 206 Partial Content");
      header("Content-Length: $new_length");
      header("Content-Range: bytes $range-$range_end/$size");
    } else {
      $new_length=$size;
      header("Content-Length: ".$size);
    }
   
    /* output the file itself */
    $chunksize = 1*(1024)*(1024); //you may want to change this
    $bytes_send = 0;
    if ($file = fopen($file, 'r'))
    {
      if(isset($_SERVER['HTTP_RANGE']))
      fseek($file, $range);
   
      while(!feof($file) &&
         (!connection_aborted()) &&
         ($bytes_send<$new_length)
           )
      {
         $buffer = fread($file, $chunksize);
         print($buffer); //echo($buffer); // is also possible
         flush();
         $bytes_send += strlen($buffer);
      }
    fclose($file);
    } else die('Error - can not open file.');
   
   die();
   }
   // END OUTPUT_FILE function