Callback Message Transfer

Request Parameters

A server-to-server callback is sent from the payment gateway to the merchant's website to confirm payments and update the payment status. This data is transmitted as an HTTP POST request to the merchant's website.

Callback Data:

data: Base64-encoded JSON document string
sign: Signature, generated based on the data string

Example:

{
    "data": "eyJ0cmFuc2FjdGlvbl9pZCI6IjMxMTExMTExIiwicmVmZXJlbmNlIjoiMTIzNDU2Nzg5IiwiYXBpX2tleSI6ImM4NGYxYWMwLWU0ZjAtMDEzMS01Mjk4LTcwOTIxYzU3YzJhMiIsImFtb3VudCI6IjMyNy43OCIsImN1cnJlbmN5IjoiVVNEIiwic3RhdHVzIjoiMyIsInN0YXR1c19uYW1lIjoic3VjY2VzcyIsInN5c3RlbV9hbW91bnQiOiIzMjcuNzgiLCJzeXN0ZW1fY3VycmVuY3kiOiJVU0QiLCJvcGVyYXRpb25fYW1vdW50IjoiMzI3Ljc4IiwiY29tbWlzc2lvbiI6IjAuMCIsInBheW1lbnRfc3lzdGVtX3R5cGUiOiJkaXJlY3QiLCJjYXJkX251bWJlciI6IjQxMTExMSoqKioqKjExMTEiLCJjYXJkX3BhbjYiOiI0MTExMTEiLCJjYXJkX3BhbjQiOiIxMTExIiwiY2FyZGhvbGRlcl9uYW1lIjoiVGFzdHkgVGVzdCIsInByb2Nlc3NpbmdfZXJyb3JfbXNnIjoiIiwiYXV0aG9yaXphdGlvbl9jb2RlIjoiIiwicGFyYW1zIjoie1widXNlcl9pZFwiPVx1MDAzZVwidGVzdF91c2VyXCIsIFwidXNlcl9lbWFpbFwiPVx1MDAzZVwidGVzdEB0ZXN0LmNvbVwiLCBcImZsYWdfZ2V0X3VybFwiPVx1MDAzZVwiMVwifSJ9",
    "sign": "68e271b78aa3aa29f1c57f1894248b76"
}

Signature check (PHP example):

hash_hmac('md5', $_POST['data'], $secret_key) === $_POST['sign'])

Where:

secret_key - shop password

JSON Callback Parameters

Parameter	Description
transaction_id	A unique transaction identifier in the payment gateway system.
reference	A unique order number in the shop system.
api_key	Shop key (identifier).
amount	Basic payment price.
currency	Good’s price currency. Possible values: EUR, USD.
status	Processing status: 0 – Transaction is created (not processed, User is redirected to finish a payment, e.g., at 3DS verification); 1 – Successful authorization (funds hold); 2 – Successful unlock of funds; 3 – Successful payment; 4 – Successful refund; 8 – Processing incomplete; 98 – Expired (transaction expired); 99 – Processing error (unsuccessful payment).
status_name	Status description
system_amount	Final price, which is paid by User including a payment provider commission.
system_currency	Payment system currency.
operation_amount	Actual transaction’s price.
commission	Payment system commission value (currency is system_currency).
payment_system_type	Payment system type.
card_number	Primary Account Number (Optional, depends on connection type and acquirer).
card_pan6	First 6 digits of card number.
card_pan4	Last 4 digits of card number.
cardholder_name	Cardholder name (Optional, depends on connection type and acquirer).
processing_error_msg	Processing error (if the processing status is 99).
authorization_code	Payment system authorization code (Optional).
pay_token	Token for recurrent payment formation (Optional, depends on payment gateway settings).
params	Merchant’s parameters.
refund_init_type	During a refund operation, a sign is generated initiator: api => 0 - Refund via API front => 1 - Refund via website admin => 2 - Refund via back-office

The merchant's website should respond to the callback with the OK string.

The payment gateway will resend the callback if the Merchant website doesn’t respond with the OK string.

API Reference

You can view a Reference API implementation for this method at this link