function download($file_source, $file_target) {
      $rh = fopen($file_source, 'rb');
      $wh = fopen($file_target, 'wb');
      if ($rh===false || $wh===false) {
              // error reading or opening file
              return false;
      }
      while(!feof($rh)) {
              if (fwrite($wh, fread($rh, 1024)) === FALSE) {
                 // 'Download error: Cannot write to file ('.$file_target.')';
                 return false;
              }
      }
      fclose($rh);
      fclose($wh);
      // No error
      return true;