Task 5: Add to Cart
The customer entered quantity will be checked against the product available stock. If
the required quantity is available, the customer order will be added to the shopping
cart. Otherwise, appropriate message indicating unavailable required quantity will be
displayed. Total for each item is also displayed (unit price * quantity). PHP sessions
can be used to achieve this functionality

Task 6: Checkout

Customer can check out by clicking checkout button in the product detail page or
checkout (can be a shopping cart image) available on every page of the web
application.
Customer orders will then be displayed in the checkout page. The customer will be
allowed to delete, modify quantity of any order or delete all orders (empty shopping
cart).
The customer can also buy all products in the shopping cart.