src/Airbrake/EventHandler.php
public function onException(\Exception $exception)
    {
        if ($this->shouldNotifyException($exception)) {
            $this->airbrakeClient->notifyOnException($exception);
        }

        return true;
    }
public function onException(\Exception $exception)
    {
        if ($this->shouldNotifyException($exception)) {
            $this->airbrakeClient->notifyOnException($exception);
        }

        return true;
    }
Catches uncaught exceptions.

@see http://us3.php.net/manual/en/function.set-exception-handler.php
@param \Exception $exception
@return bool