WorldPay Payment Module

This is an updated WorldPay module based on all prior contributions by, and not limited to Stuart Cutting, Ian Davidson, Robert N Wood, Mark Keith Evans, Brian Kiggin, Neil Millard, the authorizenet.php, secpay.php and paypal.php modules included in OSC 2.2 CVS 25 Dec 2002. All creadit to those authors, especially Ian and David for all the work they've done in the forums as well.

I've almost re-written this module from scratch, trying to make it easier to understand with comments and to make it work with OSC 2.2 CVS snapshot dated 25 Dec 2002. Prior versions of the module were not compatible with the updated OSCommerce routines, requiring complex workarounds.

Please note : This has not been tested in a live environment. Why then have I done this? I came across OSCommerce a week ago, and being in South Africa, WorldPay is the only gateway I can use here as a Trader not having a merchant account.

I wanted to make sure that before I implemented the store for myself, that it would work with Worldpay. After spending much time dissecting code and teaching myself how it all works, I got round to implementing V3 of the Worldpay module, only to find the solution wasn't entirely perfect, due to not making use of Worldpay's Callback feature.

I think I have managed to get it working in this module. I'm not a WorldPay customer, and as such am releasing this module as BETA in the hopes that programmers who are more clued up than I am can make use of this module and clean / fix it and re-release it as a contribution that is stable and that works in a live environment.