PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

618 Chapter 28 Building a Shopping Cart
This script begins by including book_sc_fns.php, the file that includes all the function
libraries for this application.
After that, you must begin a session.This is required for the shopping cart functionality
to work. Every page in the site will use the session.
The index.php script also contains some calls to HTML output functions such as
do_html_header() and do_html_footer() (both contained in output_fns.php). It also
contains some code that checks whether the user is logged in as an administrator and
gives her some different navigation options if she is; we return to this feature in the section
on the administration functions.
The most important part of this script is
// get categories out of database
$cat_array = get_categories();
// display as links to cat pages
display_categories($cat_array);
The functions get_categories() and display_categories() are in the
function libraries book_fns.php and output_fns.php, respectively.The function
get_categories() returns an array of the categories in the system, which you then pass
to display_categories(). Let’s look at the code for get_categories(), shown in
Listing 28.3.
Listing 28.3 get_categories() Function from book_fns.php—Function That
Retrieves a Category List from the Database
function get_categories() {
// query database for a list of categories
$conn = db_connect();
$query = "select catid, catname from categories";
$result = @$conn->query($query);
if (!$result) {
return false;
}
$num_cats = @$result->num_rows;
if ($num_cats == 0) {
return false;
}
$result = db_result_to_array($result);
return $result;
}