Unique session_id's for shopping cart

[lwr]

I'm brand new to PHP as of about 3 weeks ago so much of this stuff is Greek to me. I'm going through a book on PHP, MySQL, and Web Dev. I'm in an online store chapter. The code my book gives me doesn't quite work. With my shopping cart, I need a new session value each time someone comes to my cart. Currently, if you add something to the cart and go to a different computer you can view the contents of the cart.

What should I place in my code to make it so that each time a visitor is assigned a unique id? What route do I need to take to accomplish this?

I currently have:
$sess = $_SESSION['session_id'];
but this gives a single session id.

I appreciate any help!
Luke

[laserlight]

Ah, but the session id is different for each visitor.

[lwr]

That's what I thought would happen. But when I added something to the cart on this computer and went to a different computer and tried to view the contents of the cart, I'd see what I'd added while on the first computer.