<?php
// configure.php
use Payum\Core\GatewayFactoryInterface;
use Payum\Core\Model\Payment;
use Payum\Core\PayumBuilder;

$paymentClass = Payment::class;
$gatewayName = 'adyen';

$defaultConfig = [
    'factory' => $gatewayName,
    'sandbox' => true,
    // Spec
    'skinCode' => '',
    'merchantAccount' => '',
    'hmacKey' => '',
];

$payum = (new PayumBuilder())
    ->addGatewayFactory($gatewayName, function(array $config, GatewayFactoryInterface $coreGatewayFactory) {
        return new \Payum\Adyen\AdyenGatewayFactory($config, $coreGatewayFactory);
    })

    ->addGateway($gatewayName, $defaultConfig);

    ->getPayum()
;

<?php
// src/Acme/PaymentBundle/AcmePaymentBundle.php

namespace Acme\PaymentBundle;

use Payum\Adyen\Bridge\Symfony\AdyenGatewayFactory;
use Symfony\Component\HttpKernel\Bundle\Bundle;
use Symfony\Component\DependencyInjection\ContainerBuilder;

class AcmePaymentBundle extends Bundle
{
    public function build(ContainerBuilder $container)
    {
        parent::build($container);

        $extension = $container->getExtension('paum');
        $extension->addPaymentFactory(new AdyenGatewayFactory());
    }
}