Accept WeChat Pay with a server-side-only integration

Build your own payment form to add WeChat Pay to your checkout page

Overview

WeChat Pay doesn’t require any input from the customer on the merchant website. The customer must be redirected to WeChat Pay to provide the required information to process the transaction. After that, the customer is redirected back to the merchants website displaying the result of the payment.

Before you begin

• Follow the steps in Get started guide to setup your environment.
• Familiarize yourself with the general Server side-only integration guide.

Step 1: Create a payment type resource

server side

When creating the payment type WeChat Pay, you need to send a request to the Unzer API. The response will contain an id, later referred to as typeId. You need this typeId to perform the transaction.

POST https://api.unzer.com/v1/types/wechatpay

Body: {}

$unzer = new UnzerSDK\Unzer('s-priv-xxxxxxxxxx');

$wechatpay = new UnzerSDK\Resources\PaymentTypes\Wechatpay();
$wechatpay = $unzer->createPaymentType($wechatpay);

Wechatpay wechatpay = new Wechatpay();
Unzer unzer = new Unzer(new HttpClientBasedRestCommunication(), "s-priv-xxxxxxxxxx");
wechatpay = unzer.createPaymentType(wechatpay);

The response will look similar to the following example:

{
    "id": "s-wcp-otvqlpgqsh7u",
    "method": "wechatpay",
    "recurring": false,
    "geoLocation": {
        "clientIp": "127.0.0.143",
        "countryCode": "DE"
    }
}

For a full description of WeChat Pay payment type creation check API reference.

Step 2: Make a payment

server side

Make a charge transaction

Now, make a charge transaction with the Wechatpay typeId that you created and the returnUrl leading back to your shop after the payment is finished on the external page. With the charge transaction an amount is requested but is not yet transferred. Initially the transaction will be pending and a payment resource is created.

POST https://api.unzer.com/v1/payments/charges
   
{
  "amount" : "20",
  "currency": "EUR",
  "returnUrl": "https://www.my-shop-url.de/returnhandler",
  "resources" : {
    "typeId" : "s-wcp-jldsmlmiprwe"
  }
}

$unzer = new Unzer('s-priv-xxxxxxxxxx');
$wechatpay = $unzer->fetchPaymentType('s-wcp-0ajzmaxcuvhc');
$charge = $wechatpay->charge(20.0, 'EUR', 'https://www.my-shop-url.de/returnhandler');

Unzer unzer = new Unzer("s-priv-xxxxxxxxxx");
Charge charge = unzer.charge(BigDecimal.ONE, Currency.getInstance("EUR"), "s-wcp-0ajzmaxcuvhc", new URL("https://www.my-shop-url.de/returnhandler"));

The response looks similar to the following example:

{
    "id": "s-chg-1",
    "isSuccess": false,
    "isPending": true,
    "isError": false,
    "redirectUrl": "https://payment.unzer.com/v1/redirect/wechatpay/s-sGYdGywWpxzW",
    "message": {
        "code": "COR.000.100.112",
        "merchant": "Request successfully processed in 'Merchant in Connector Test Mode'",
        "customer": "Your payments have been successfully processed in sandbox mode."
    },
    "amount": "20.0000",
    "currency": "EUR",
    "returnUrl": "https://www.my-shop-url.de/returnhandler",
    "date": "2021-05-10 00:51:03",
    "resources": {
        "paymentId": "s-pay-131937",
        "traceId": "70ddf3152a798c554d9751a6d77812ae",
        "typeId": "s-wcp-jldsmlmiprwe"
    },
    "paymentReference": "",
    "processing": {
        "uniqueId": "31HA07BC8157BD2BC04D483EFA914465",
        "shortId": "4845.3426.1987",
        "traceId": "70ddf3152a798c554d9751a6d77812ae"
    }
}

For a full description of the charge transaction, refer to the relevant server-side integration documentation page: Charge a payment (direct API calls), Charge a payment (PHP SDK), Charge a payment (Java SDK).

Forward the customer to external payment page

After you charge the WeChat Pay resource, implement the following flow:

1. Forward the customer to the redirectUrl returned in the response to your Charge request.
2. The customer is forwarded to the WeChat Pay payment page.
3. After a successful payment or abort on the WeChat Pay page, the customer is redirected to the returnUrl specified in the initial Charge call.

Step 3: Check status of the payment

server side

Once the customer is redirected to the returnUrl, you can fetch the payment details from the API, by using the resources.paymentId from the charge response above to handle the payment according to its status. If the status of the payment is completed , the payment process has been finished successfully and can be considered as paid. Check all possible payment states here.

GET https://api.unzer.com/v1/payments/{payment_ID}

{
    "id": "s-pay-131937",
    "state": {
        "id": 1,
        "name": "completed"
    },
    "amount": {
        "total": "20.0000",
        "charged": "20.0000",
        "canceled": "0.0000",
        "remaining": "0.0000"
    },
    "currency": "EUR",
    "orderId": "",
    "invoiceId": "",
    "resources": {
        "customerId": "",
        "paymentId": "s-pay-131937",
        "basketId": "",
        "metadataId": "",
        "payPageId": "",
        "traceId": "70ddf3152a798c554d9751a6d77812ae",
        "typeId": "s-wcp-grpucjmy5zrk"
    },
    "transactions": [
        {
            "date": "2021-05-10 00:51:03",
            "type": "charge",
            "status": "success",
            "url": "https://api.unzer.com/v1/payments/s-pay-131937/charges/s-chg-1",
            "amount": "20.0000"
        }
    ]
}

Step 4: Display the payment result

client side

Use the information from the Check status of the payment step to display the payment result to your customer.
This can be the success or error page of your shop. If something went wrong, you can use the client message from the API response and show it to the customer.

Manage payment

server side

For more details on managing WeChat Pay payments, such as refunding them, see Manage WeChat Pay payments.

Notifications

We recommend subscribing to the payment event to receive notifications about any changes to the payment resource. As soon as the event is triggered you should fetch the payment and update the order status in your shop according to its status.

  {
    "event":"payment.pending",
    "publicKey":"s-pub-xxxxxxxxxx",
    "retrieveUrl":"https://api.unzer.com/v1/payments/s-pay-774",
    "paymentId":"s-pay-774"
  }

For more details on implementing webhooks to receive notifications, see Notifications page.

Error handling

All requests to the API can result in an error that should be handled. Refer to the Error handling guide to learn more about Unzer API (and other) errors and handling them.

Test & go live

You should always test your integration before going live. First perform test transactions using test data. Next, check against Integration checklist and Go-live checklist to make sure the integration is complete and you’re ready to go live.

See also

• Manage API resources:
  • Manage API resources (direct API calls)
  • Manage API resources (PHP SDK)
  • Manage API resources (Java SDK)
• Unzer API basics