mobile texting app question

All, I am working on the design for an app that uses mobile phone texting to make payments, but I am having some trouble finding out how the whole mobile process works. I grow the CSC (common short code) set up and them acting as a clearing house, but can anyone point me to some docs on how the process works. From the user attempting to text a payment to my site getting the data? Its kinda off topic, other than the entire site / app will be php based. Googling doesn't get me that far, but it might be more of a not knowing exactly what its called to be able to narrow the search. Appreciate any replies. -- Bastien Cat, the other other white meat