public function fulfillOrder($get) {
        global $usces;

        $transactionId = $get['transactionId'];
        $order_data = get_option($transactionId);
        $_SESSION['usces_entry'] = $order_data['usces_entry'];
        $_SESSION['usces_member'] = $order_data['usces_member'];
        $_SESSION['usces_cart'] = [];

        // reserialize cart for usces' cart class
        foreach ($order_data['usces_cart'] as $obj) {
            $_SESSION['usces_cart'][$obj['serial']] = [
                'quant' => $obj['quantity'],
                'price' => $obj['price'],
            ];
        }

        $payload = [
            'amount' => $order_data['total'],
            'currency' => $order_data['currency'],
        ];
        $confirmres = $this->module->api->confirm($payload, $transactionId);
        if ($confirmres instanceof GenericError) {
            // remove tracking
            delete_option($transactionId);
            $this->error = $confirmres;
            $this->errorPageRedirect();
            return;
        }

        $results = [];
        $usces_entries = $usces->cart->get_entry();
        $payments = $usces->getPayments($usces_entries['order']['payment_name']);
        /**
         * Welcart filter
         *
         * @ignore
         */
        $nonacting_settlements = apply_filters('usces_filter_nonacting_settlements', $usces->nonacting_settlements);

        $res = usces_check_acting_return_duplicate($results);
        if ($res != null && !in_array($payments['settlement'], $nonacting_settlements)) {
            usces_log('order processing duplicate : acting=' . $order_data['acting'] . ', order_id=' . $res, 'acting_transaction.log');
        }
        $order_id = usces_reg_orderdata($results);

        if (empty($order_id)) {
            // remove tracking
            delete_option($transactionId);
            $this->error = $this->module->clientErrorStore->getErrorCodeMap()[ErrorStore::INTERNAL_SERVER_ERROR];
            $this->errorPageRedirect();
            return;
        }

        $state = $order_data['capture_now'] ? TransactionState::CAPTURED : TransactionState::AUTHORIZED;
        $line_order_data = [
            'transactionId' => $transactionId,
            'total' => $order_data['total'],
            'currency' => $order_data['currency'],
            'line_request_res' => $order_data['line_request_res'],
            'line_confirm_res' => $confirmres,
        ];
        OrderMeta::registerOrderMeta(new TransactionState($transactionId, $state), $line_order_data, $order_id);

        $mail_res = usces_send_ordermail($order_id);

        // remove tracking
        delete_option($transactionId);
        $this->completionPageRedirect();
    }