This is a simple cart system with PHP and SQL.

For try this,

1. You should register (or login) with multiple profiles.
2. After login you can see the home page. Then visit the Add Products page.
3. Add products with all of those multiple profiles (those profiles pose as sellers and buyers).
4. Then go to the home page again with one of account you created, visit the products page and after you can see all of products added by all profiles.
5. You can add those products to your cart with 'Add to cart' button.
6. Then go to the home page again and visit the cart page. You can see all of products added by you to your cart.