API to preface gateway transactions (API)

My project is very simple, This project needs to be started on TODAY, do NOT bid if you are going to schedule to work on it later. I currently have an application that is currently working: it is used to redirect clicks. (attached is a screenshot of table in database) It has 2 modes, whitelist and blacklist. it deciphers and decides a click is blacklisted based on: -Token -Sub id (only let a defined sub clear as white) -User Agent -GeoIp -DNS PTR (and validates forward lookup) -Hit Frequency -IP/Network database I need to turn this into a service (API) that is placed before a payment gateway. if success redirect to success url For example right now someone fills out order page -> gateway -> gateway response gateway Customer fills out order page -> NEW API -> NEW API RESPONSE ->gateway -> if fail echo decline response I will provide the php file the decides where the file goes and has all the logic. This will need a document explaining how to use the restful API.