Shopping Cart Hell

New to php and mysql

Here's my dilemma:
I created a site for a photographer over a year ago using the Joomla
CMS. His customers login and see their own specific gallery of
images.

Now he wants his customers to be able to order prints online. I
figured that I could add some code to the php page in the gallery
script that shows the image. Just some basic options, print size,
quantity, add to cart button...

I wouldn't know how to get that info into a persistent shopping cart
using sessions or cookies.

I don't need help with the checkout process, I'm confident I can
handle that on my own. Just need some direction with the ordering and
session cart.

Any input is greatly appreciated.

Thanks!

ktstone
.