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

Implementing the Online Catalog
621
This script is similar in structure to the index page, except that you retrieve books
instead of categories.
You start with session_start() as usual and then convert the category ID you have
been passed into a category name by using the get_category_name() function as follows:
$name = get_category_name($catid);
This function, shown in Listing 28.7, looks up the category name in the database.
Listing 28.7 get_category_name() Function from book_fns.php—Function That
Converts a Category ID to a Category Name
function get_category_name($catid) {
// query database for the name for a category id
$conn = db_connect();
$query = "select catname from categories
where catid = '".$catid."'";
$result = @$conn->query($query);
if (!$result) {
return false;
}
$num_cats = @$result->num_rows;
if ($num_cats == 0) {
return false;
}
$row = $result->fetch_object();
return $row->catname;
}
After you have retrieved the category name, you can render an HTML header and proceed
to retrieve and list the books from the database that fall into your chosen category,
as follows:
$book_array = get_books($catid);
display_books($book_array);
The functions get_books() and display_books() are extremely similar to the
get_categories() and display_categories() functions, so we do not go into them
here.The only difference is that you retrieve information from the books table rather
than the categories table.