My online shopping project i also faced same problem. after lot of googling i find the solution. Response is provided using POST method to the URL defined under ReturnURL parameter in the payment request. $response['ResponseCode'] == 0 means transaction successfully completed. Other than 0 value transactions failed.
Read below article to solve the problem. In this article clearly explained how to integrate ebs payment gatway in php. try it.
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EBS Payment Integration using PHP