Should be a simple script that will accept post of billing information, and based on a preset variable ($processtype) will automatically process with:
paypal, worldpay, [login to view URL], 2checkout, egold.
each should provide a simple redirect if the payment processed to a "[login to view URL]" page, if it fails then should redirect to a "[login to view URL]" page (this will provide the form again with the items filled out.
should be set with each payment processing type in a seperate file as follows:
[login to view URL] (paypal processor)
[login to view URL] (worldpay processor)
[login to view URL] ([login to view URL] processor)
[login to view URL] (2checkout processor)
[login to view URL] (egold processor)
I will soon provide a skeleton page and directory setup for you.