Creating a virtual wallet to display balance in a store I have a store that uses bitcoin as a payement. 
I want to make users deposit to their balance in the site, as I saw in many sites, 
a bitcoin address is generated for each user to deposit funds to it, and use his dashboard in the site to withdaw it to his BTC address anytime.
I am using PHP. How to do it?
It is a way much better practice to generate a new address for every new order and not per user, as this would imply address reuse for returning customers, which is generally discouraged. Then the users won't have to keep their funds on your website and will only pay the exact amount for each order.

You can take a look at these open source projects for bitcoin written in PHP for starters.