public function createPackage()
    {
        if (!$this->getEventCategory()) {
            throw new MissingTrackingParameterException('event category must be set');
        }

        if (!$this->getEventAction()) {
            throw new MissingTrackingParameterException('event action must be set');
        }

        return array(
            't' => 'event',
            'ec' => $this->getEventCategory(),
            'ea' => $this->getEventAction(),
            'el' => $this->getEventLabel(),
            'ev' => $this->getEventValue()
        );
    }