18.1 Code Overview
This section outlines the functions of
the scripts that implement the shopping cart and winestore home page.
The cart is implemented in the
cart/showcart.php,
cart/addtocart.php,
cart/emptycart.php, and
cart/updatecart.php scripts. The home page is
implemented as index.php. The database-based
cart management process is discussed later in Section 18.3.
The script
cart/showcart.php
is the only shopping cart
script that presents output to the user. It shows the
cart's current contents using a form in an HTML
table environment that allows the user to modify the quantity of any
of the items. If the cart contains no items, a message is shown
instead. Figure 18-1 shows an example of a cart
containing four items.
If the user modifies any quantity in the cart, then he must click on
the Update Quantities button to write the change
to the database. This submits the form and requests the script
cart/updatecart.php
, which processes the
variables and values passed with the GET method
and updates the quantities. Setting a quantity to zero deletes the
item. If the user wants to completely empty the cart, he can click on
Empty Cart which requests the
cart/emptycart.php script.
cart/updatecart.php and
cart/emptycart.php don't
produce any HTML output, but instead redirect the browser back to
cart/showcart.php.
The
cart/addtocart.php
scripts adds a quantity of
a wine to the cart. It can be requested from both the home page and
the search/search.php script discussed in Chapter 20. The script expects two parameters to be
passed: the wine to be added (referenced by its
wine_id) and the quantity to add. The script
handles the three different cases that can occur when adding a wine
item to the cart:
The item is the first to be added to an empty cart, and a new cart
needs to be created before the item is added. The item is a new item being added to an existing cart. The item is already in the cart and the user is adding an additional
quantity.
When a wine is added for the first time to the cart, the script also
discovers the cheapest price of that wine in the inventory (as per
the requirements in Chapter 16).
The homepage script index.php displays the three
wines that have most-recently been reviewed by a wine writer. With
each of these wines, it includes embedded links that can be clicked
on to add one or a dozen bottles to the shopping cart using the
cart/addtocart.php script. The home page also
displays a welcome message, and buttons that allow the user to search
the wines, become a member or amend member details, and login or
logout. The home page is shown in Figure 18-2.
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