payment.php

См. документацию.

<?if (!defined("B_PROLOG_INCLUDED") || B_PROLOG_INCLUDED !== true)
    die();
 
$entityId = CSalePaySystemAction::GetParamValue("PAYMENT_ID");
list($orderId, $paymentId) = \Bitrix\Sale\PaySystem\Manager::getIdsByPayment($entityId);

$order = \Bitrix\Sale\Order::load($orderId);

$paymentCollection = $order->getPaymentCollection();

$payment = $paymentCollection->getItemById($paymentId);
 
$data = \Bitrix\Sale\PaySystem\Manager::getById($payment->getPaymentSystemId());
 
$service = new \Bitrix\Sale\PaySystem\Service($data);
$service->initiatePay($payment);