Payment Merchant Integration on Travel website

Looking for someone to integrate Payments Merchants to process payments via our Payment Gateway on our Travel website. Looking for a developer who has experience in server-side scripting with languages such as PHP or ASP, or that an off-the-shelf software package is being used that has in-built or plug-in support for the Payment Gateway.
We have an Integration guide from our Merchant and are happy to share it with the right candidate.