code: protected function notify($callbackNotification, $message, $severity)
      {
          $callableName = '';
          if (is_callable($callbackNotification, false, $callableName)) {
              call_user_func($callbackNotification, $message, $severity);
          }
      }
docs: Sends a notification.
  
  @param callback $callbackNotification Callback to send notification
  @param string $message
  @param integer $severity