Process the answer from external Payment Gateway

Hello.
I developed a custom plugin that implement a new payment method.
Inside the “process_payment()” function I do basically 2 steps:

– Insert a payment “to_do” into the Payment server (via a SOAP call)
[I receive a “payment_key” as answer]

– Redirect the customer to the external url, so it can do the payment.

My external payment gateway accept these parameters in Post:

• payment_key
  (obviously, so the customer is redirect to HIS order to pay)
• ret_url
  This is the URL where the customer will be redirected after the payment.
  I set it with “$this->get_return_url( $order )”.
  In the URL parameters, after redirect back to the e-commerce there is a “result” parameter, that inform the e-commerce about the payment success (OK – ERROR)

Problem:
To “send” the customer “outside” to process the payment, I used “return” with array:

	
   return array(
      'result' => 'success',
      'redirect' => $PPAurl
   );

But being the “result” parameter already set to “success”, any response I get from the gateway (as URL parameters), when the browser come back to my e-commerce, I always land on the “Order received” page. The cart is empty, and all seems good.

How can I process the answer (in the url parameters) from the gataway, when I return to my e-commerce after the “external” payment?

How can I “go outside” the ecommerce for the payment, without set to “success” my payment return?

Thanks Everyone.

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