This script doesn't include any payment method or payment page. This script lists manually added products, you can add that products to your shopping cart, remove them, change quantity via sessions. Also this script is a good exercise to understand PHP session arrays. You can easily add - remove items from shopping cart, all data stored in sessions and system not uses a database. In source code, you can add - remove products manually. You have to know basic HTML for this. If you wish, you can code for database integration.