Asynchronous callback Notification. Although there is a callback function for successful payment, the data obtained cannot be completely correct because it is a callback from the client. For example, if money is given due to delay in entry, it is not considered payment.
all payments are subject to asynchronous notification

step back notification.

"after the payment is finished, the payment platform will send the transaction result to the merchant website in the background according to the notify_url address. Because the front-end response is subject to the user's network fluctuations, you need to notify the payment result of the order with the background result. As for the problem of being called in disguise, the front-end response needs to be notified of the payment result with the background result," the payment platform will send the transaction result to the merchant website in the background after the payment is completed. When the payment platform requests notification from the merchant platform, there will be a signature generated by the platform public key and the merchant private key, and the merchant platform will respond "