shopping cart payment submission

[jmkimmel]

I got involved building a shopping cart for someone and they are using Orbital Gateway by Paymentech to verify credit card transactions. This is good news in that I don't have to be quite as concerned with security as if I was trying to do it within FileMaker. This site will accept an XML post action. I am picturing having the total from the cart entered into a form that the user then adds their credit information to. Would I then write the xml information into the action, or how should the information from the form get transmitted in the form of the post to the site?