I have been going through all of the different PayPal integration options and trying to decide which will be the best one for this particular application. I realized that I really want to give users a few options for payment. For example, it might be more convenient to enter their credit card information rather than being sent over to PayPal, or they may have already setup their Google Checkout and so want to use that.

So that brings me fairly quickly to the realization that maybe I don't want to program one or two or three API integrations myself and I should look at some shopping cart software. However, we really don't need a whole shopping cart -- we will have a specific form and some other custom coding and the only part of the shopping cart we would really use would be the checkout page to handle accepting payment/integrating with PayPal/Google Checkout/Authorize.net.

I like how simple eJunkie makes things and the fact that it accepts PayPal and Google Checkout and Authorize.net. The problem is that the Add To Cart buttons aren't going to cut it. I need to be able to programmatically enter items into the cart.

Maybe I can just use an open source PHP shopping cart and skip the store front somehow.