319417 PHP Shopping Cart FIX

I had a custom built shopping cart that works great except for one small flaw.. When I buy an item say a specific t-shirt in one size and color for example: Red Large Baseball shirt... QTY 1 Then I go back and buy the same baseball shirt that is the blue and small.. It shows up in the view cart section as: 2 small blue baseball shirts When it should show the details of the individual items purchased like this: 1 large red baseball shirt 1 small blue baseball shirt That's the only problem I have with it. I need someone who is good at php. No beginners wanted. This site is live so we need to make the fix quick and without any real downtime. I think it's a small