public function saveAsFile()
 {
     if (func_num_args() === 1) {
         $pathAndFilename = func_get_arg(0);
     } else {
         if ($this->filename) {
             $pathAndFilename = $this->filename;
         } else {
             new mb_exception(__FILE__ . ": saveAsFile(): must specify a filename!");
             return false;
         }
     }
     //delete all entries which are more than MAX_ENTRIES from RSS!
     return administration::saveFile($pathAndFilename, $this->__toString());
 }