Thanks to everyone who gave me advice in my last post. Let me tell you a bit about what I'm trying to do. I'm building an online store using PHP/MySQL. I have the account creation script done, and a customer survey script done. I need to build a shopping cart, and an inventory management system for myself to make it easier to add/edit merchandise. I just taught myself PHP recently, for the purpose of this project, so forgive me if I ask what might seem like a stupid question.

Is it safe to store customer's credit card numbers in the database?
What security issues in general do I need to be careful of with an online store?
Can anyone recomend a site that offers a tutorial or some advice?
Anyone have any random advice for me at all?

I know I could just download someone else's code but thats no fun :)