Develope an open cart payment gateway extension

I need for my open cart based website a payment gateway: [login to view URL] Extensione must be compiant with open cart 2.x versions. To greatly simplify your work I'll supply you with the attached working php example. It uses the following parameters: $shopLogin = 'gespayXXXXX'; //YOUR SHOP LOGIN Eg. production code '9000001' , test code 'gespay0001' $currency = '242'; //payment currency 242 -> Euro $amount = '0.05'; //payment amount $shopTransactionID = 'YourOrderIdentifier'; //your payment order identifier $amount and $shopTransactionID should be got from open cart checkout session Scurrency will always be 242 $shopLogin: just use test code gespay0001 and then let me know in production how to manage such value Once you got the encrypted variable a and b, a redirect to payment server is required (instead of the form you see in the example). Finally open cart must manage server response (OK or KO)