PayPal IPN/PDT with credit card

Question

I am writing an IPN application for doing theater seat reservations. I place a temporary hold on the seats before going off to PayPal. When the IPN handler is called and detects a successful payment, the seats are reserved permanently.

The "return" parameter for my PayPal brings the customer back to the reservations application. Because the IPN handler may not have been called yet, the customer may or may not see his seats reserved (this is probably not the best application for IPN, but I am too cheap to spring for one of the non-free methods). So I am considering incorporating PDT. The "return" parameter would then specify a URL that would first complete the reservation processing in case the IPN handler has not already been called. Here are my questions:

My understanding is that if the customer does not have a PayPal account so that he instead uses his credit card to pay for the reservation, then PDT is inoperative (why this is unimaginable). What then does PayPal do so far as honoring the "return" URL? Does PayPal ignore it entirely or does it still return to that location but without passing the "tx' parameter? In the sandbox environment, of course, you always have a PayPal account and I am obviously unable to turn on PDT in my production environment production just to see what happens when one uses a credit card to make a payment, hence my post. However, I did specify in the sandbox that I wanted to use my (dummy) credit card to pay for the reservation and the "return" URL was invoked with the "tx" parameter. This was perplexing. So when PayPal says that PDT is not meant to be used with credit cards, will PDT work anyway as long as the customer is logged on to his PayPal account or is this just a peculiarity of the sandbox?

Answer 1

I am in the opposite position here, I have PDT implemented, but because the auto return doesn't work for my users without Paypal accounts, I am looking into adding IPN to my site to supplement PDT.

As I said, auto return does not work for customers/users who do not log into a PayPal account to make a payment. They can still make a payment if you have the "PayPal Account Optional" feature turned on in your Website Payment Preferences. They are given a link to your specified return page after their payment to return to your site, but are not automatically returned, so effectively, PDT doesn't work unless the user manually returns to your site (to the appropriate page) to initiate the PDT process. I have had problems with users not returning which prevents my registration process from completing, which is why I'm also going to be adding IPN.

PDT works with credit card payments as long as the user returns or is returned to your site after the payment to initiate PDT.