I have a php web site (in progress) where you when you make a purchase it adds credits to your user account. Both Paypal and Amazon worked successfully. However, in the course of working on the site over time, I retested yesterday and Amazon purchases add credits, but for some reason Paypal purchases do not. After a purchase the user returns successfully to the site, but the credits are now not added to the user account.
Is this a Paypal issue or a php issue?