private function checkIfSuccessful(\DOMDocument $responseDoc)
    {
        $this->wasSuccessful = false;

        $list = $responseDoc->getElementsByTagNameNS(OrderService::NAMESPACE_N3, 'successfully');
        if ($list->length > 0) {
            $success = $responseDoc->getElementsByTagNameNS(OrderService::NAMESPACE_N3, 'successfully')->item(0)->nodeValue;

            $this->wasSuccessful = ($success === 'true');
        } else {
            $list = $responseDoc->getElementsByTagNameNS(OrderService::NAMESPACE_N3, 'ProcessorResponseMessage');
            if ($list->length > 0) {
                $this->wasSuccessful = ($list->item(0)->nodeValue === Sell::RESPONSE_SUCCESS);
            }

            if ($this->wasSuccessful === false) {
                $list = $responseDoc->getElementsByTagNameNS(OrderService::NAMESPACE_N3, 'TransactionResult');
                if ($list->length > 0) {
                    $this->wasSuccessful = ($list->item(0)->nodeValue === Sell::TRANSACTION_RESULT_APPROVED);
                }
            }
        }

        return $this->wasSuccessful;
    }