How to implement an external payment gateway with Prestashop? - php

Question

I need to implement an external payment gateway in Prestashop. I have to send an HTTP request as below:
<form method="post" name="payment" action="url">
blah blah....
<input name="ResponseURL" value="{$response}">
</form>
The ResponseURL is the URL provided by me to retrieve the response from the API. This is where I need to perform validation checking and redirect to the order confirmation page. (similarly to the validation front controller from ps_checkpayment module)
I have also added the hookPaymentOption
public function hookPaymentOptions($params)
{
if (!$this->active) {
return;
}
//some code here
$response = 'http://' . $_SERVER['SERVER_NAME'] . $this->_path . '/classes/response.php';
$formAction = $this->context->link->getModuleLink($this->name, 'validation', array(), true);
$this->smarty->assign([
//some code here
'response' => $response
]);
$paymentForm = $this->fetch('module:easypaymentoption/views/templates/hook/payment_options.tpl');
$newOption = new PaymentOption();
$newOption->setModuleName($this->displayName)
->setCallToActionText($this->displayName)
->setAction($formAction)
->setForm($paymentForm);
$payment_options = array(
$newOption
);
return $payment_options;
}
I'm just really clueless as to how to proceed. I've tried to link my $response to a front module controller class, but I get an error that says
Fatal error: Uncaught Error: Class 'ModuleFrontController' not found in C:\xampp\htdocs\prestashop\modules\easypaymentoption\classes\response.php:3 .
I have also tried to link to an empty php file, but by doing this I can't get the necessary information to do validation checking and redirect to the order confirmation page that I would otherwise would get by using a class that extends ModuleFrontController.
Any help is appreciated, as I've been stuck here for almost 3 days.