Integrated credit and payment system
This question is kind of client and kind of server based. Basically what I want to build for my site is a way for users to be able to receive points (which is valued the same as the dollar). To purchase items on the site, the user can use up to 50% of their points on an item and the rest they have to pay with cash.
eg. There is a power adapter that is valued at $50 and users can use up to 30 points to purchase the item. They can buy the item for 30 points and $20 cash, or 0 points and $50 cash or anything in between.
I'm thinking of using PayPal for the payment handling. So far as I know, you click on a generated link and it sends you to the Paypal payment site. So I have a few questions on how to do this.
1) What language and database type should I use if I want this be an integrated payment and membership system (ie. It automatically docks credit from user account)?
2) How do I generate the link dynamically so that the payment amount can be made on the fly and the points are automatically deducted from the user's credit?
3) What would be the best webhost for this?