On the site (MODX REVO) through Shopkeeper 3, an order is made out, when choosing online payment, the user is redirected to Yandex.Money.
After successful payment of the order, it is necessary to save in the JSON format the data of the buyer specified at the order, for further transfer to the user's account.
The order form is made through FormIt, then the data is transmitted to the cashier.
With online payments did not have to work, in what direction should I look? The Yandex API found that the data is transmitted in JSON format but in Shopkeeper the user is recorded without payment, and immediately after the order.