public function getInvitor()
    {
        $sSu = \OxidEsales\Eshop\Core\Registry::getSession()->getVariable('su');

        if (!$sSu && ($sSuNew = \OxidEsales\Eshop\Core\Registry::getConfig()->getRequestParameter('su'))) {
            \OxidEsales\Eshop\Core\Registry::getSession()->setVariable('su', $sSuNew);
        }
    }