Very small and easy project!
I use World Pay for credit cards.
To make a pament I send a very easy POST via a FORM to their website.
This includes my ID, Amount, Description, Currency, 2 Custom Fields and that is about all!
I want to be able to enter some information in a database so when a client is due for renewal I can send them a special link
[url removed, login to view]
Where I would have set 34 up in the database to be a set paymenet
with Price - Description etc......
They see a nice page and then click pay now - to send the form to world pay.