code: public function onException(\Exception $exception)
      {
          if ($this->shouldNotifyException($exception)) {
              $this->airbrakeClient->notifyOnException($exception);
          }
  
          return true;
      }
docs: Catches uncaught exceptions.
  
  @see http://us3.php.net/manual/en/function.set-exception-handler.php
  @param \Exception $exception
  @return bool