public function getPayPalSandboxApiUrl()
    {
        $url = \OxidEsales\Eshop\Core\Registry::getConfig()->getConfigParam('sPayPalSandboxApiUrl');
        if ($url) {
            $this->setPayPalSandboxApiUrl($url);
        }

        return $this->payPalSandboxApiUrl;
    }