amember - 您如何知道该产品是否曾在 AMEMBER 购买过？

Question

我还是有问题，当这个产品已经购买后，它应该进入第二次付款。不知道这是第一次付款还是第二次付款

 public function _process(Invoice $invoice, Am_Mvc_Request $request, Am_Paysystem_Result $result)
    {

        if ((float)$invoice->first_total == 0) {
            $invoice->addAccessPeriod(new Am_Paysystem_Transaction_Free($this));
            $result->setAction(
                new Am_Paysystem_Action_Redirect(
                    $this->getReturnUrl()));
            return;
        } else {

            $res = $this->getPaymentParams($invoice);

            if (!empty($res->statusCode) && $res->statusCode === "00") {

                //FIRST PAYMENT NOT DETECTED
                if ($invoice->isFirstPayment()) {
                    $a = new Am_Paysystem_Action_Redirect(REL_ROOT_URL . "/payment/" . $this->getId() . "/instructions?id=" . $invoice->getSecureId($this->getId()));
                } else {
                    $a = new Am_Paysystem_Action_Redirect(REL_ROOT_URL . "/payment/" . $this->getId() . "/rebill?id=" . $invoice->getSecureId($this->getId()));
                }

                $result->setAction($a);
            } else {
                print_rr($res);
                $result->setFailed('Connection Problem with DUITKU');
            }
        }


    }