PaymentConfig.php

<?php 

class PaymentConfig
{
	private $data = [];
	
	public function set($key, $value)
	{
		$this->data[$key] = $value;
	}
	public function get($key)
	{
		return $this->data[$key] ?? null ;
	}
	
	public function has($key)
	{
		return isset($this->data[$key]);
	}
}

RecurringPayment.php

<?php 

interface RecurringPayment
{
	public function create(PaymentConfig $config);
	public function setResponse($data);
	public function getResponse();
}

RecurringPaymentController.php

<?php 

interface RecurringPaymentController
{	
	public function confirm();
	public function callback();
}