Omnipay

<?php

public function pay(Request $request, $id)
    {
        $order = Order::where('user_id', $request->user()->id)->findOrFail($id);
        $paymentMethod = $request->payment_method;
        $payment = $order->payment()->create([
            'method' => $paymentMethod,
            'status' => 'payment_new',
//            'amount' => $order->amount,
        ]);

        // https://omnipay.thephpleague.com/gateways/build-your-own/
        // Merchant Site - The website or application that initiates the payment (магазит, сайт для создания заказа/плтежа)
        // Merchant - The owner or operator of the Merchant Site (владелец сайта магазина)
        // Payment Gateway -  The remote payment processing system that handles the communication and transfer of funds between the Merchant Site (платежная система)
        // Off-site gateways such as PayPal Express, where the customer is redirected to a third party site to enter payment details
        // On-site (merchant-hosted) gateways such as PayPal Pro, where the customer enters their credit card details on your site

        $params = [
            'amount' => $order->amount,
            'currency' => 'RUB',
            'transactionId' => $order->number, // Is the Merchant’s reference to the transaction - so typically the ID of the payment record in the Merchant Site’s database
            'description' => "Some description (order $order->number)",
            'interface' => 'web',
//        'action' => 'payway',
//        'payway' => 'privat24_liqpay_merchant3_uah',
            'returnUrl' => route('pay-successful-page', [$paymentMethod, 'order' => $order->id]), // перенаправление клиента после платежа
            'returnMethod' => 'GET',
            'cancelUrl' => route('pay-failed-page'), // перенаправление клиента после не успешного платежа
            'cancelMethod' => 'GET',
            'notifyUrl' => route('pay-successful-page'), // уведомление от Payment Gateway для Merchant Site о платеже
            'notifyMethod' => 'POST',
//            'returnUrl' => "https://mydomain.com/payment/interkassa/success?order=$order->number",
//            'returnMethod' => 'GET',
//            'cancelUrl' => 'https://mydomain.com/payment/interkassa/cancel',
//            'cancelMethod' => 'GET',
//            'notifyUrl' => 'https://mydomain.com/payment/interkassa/notify',
//            'notifyMethod' => 'POST',
        ];

        $response = \Omnipay::gateway($paymentMethod)->purchase($params)->send();

        if ($response->isSuccessful()) {
            dump('payment was successful: update database');
            // payment was successful: update database
            print_r($response);
        } elseif ($response->isRedirect()) {
            dump('redirect to offsite payment gateway');
            // redirect to offsite payment gateway
            return $response->getRedirectResponse();
        } else {
            dump('payment failed: display message to customer');
            // payment failed: display message to customer
            echo $response->getMessage();
        }
    }

Upgrade guide for omnipay/common https://github.com/thephpleague/omnipay-common/blob/master/UPGRADE.md

completeRegistration() = completePurchase() = completeAuthorize() is deprecated, use acceptNotification(array $parameters = [])
    if ($gateway->supportsAcceptNotification()) { //supportsCompletePurchase, supportsPurchase, supportsCompleteAuthorize,...
        \Log::info('support AcceptNotification');
    }

    completePurchase() - когда пользователь возвращается с плаетжки на страницу магазина
    acceptNotification() - когда платежка возвращает результат платежа в магазин


    // authorize($options) - authorize an amount on the customer's card
    // completeAuthorize($options) - handle return from off-site gateways after authorization
    // capture($options) - capture an amount you have previously authorized
    // purchase($options) - authorize and immediately capture an amount on the customer's card
    // completePurchase($options) - handle return from off-site gateways after purchase
    // refund($options) - refund an already processed transaction
    // void($options) - generally can only be called up to 24 hours after submitting a transaction
    // acceptNotification() - convert an incoming request from an off-site gateway to a generic notification object for further processing



public function completeRegistration(array $parameters = array())
{
    return $this->createRequest('\Omnipay\SagePay\Message\ServerTokenRegistrationCompleteRequest', $parameters);
}
public function completeAuthorize(array $parameters = array())
{
    return $this->createRequest('\Omnipay\SagePay\Message\ServerCompleteAuthorizeRequest', $parameters);
}
public function completePurchase(array $parameters = array())
{
    return $this->completeAuthorize($parameters);
}



public function acceptNotification(array $parameters = array())
{
    return $this->createRequest('\Omnipay\SagePay\Message\ServerNotifyRequest', $parameters);
}
$gateway = \Omnipay::gateway($gateway);
$response = $gateway->acceptNotification($request->all())->send();
$response->getTransactionId(); // the reference set by the originating website if available.
$response->getTransactionReference(); // A reference provided by the gateway to represent this transaction
$response->getTransactionStatus(); // Current status of the transaction, one of NotificationInterface::STATUS_*
$response->getMessage(); // Additional message, if any, provided by the gateway
$response->isSuccessful(); // is the response successful?
$response->isRedirect(); // is the response a redirect?

// update the status of the corresponding transaction in your database

fomvasss/Omnipay.md