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

Solution Overview
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if(!eregi('^[a-z]+$', $mode)) {
// mode must be alphabetic
$mode = 'Books';
}
$page=intval($page); // pages and browseNodes must be integers
$browseNode = intval($browseNode);
// it may cause some confusion, but we are stripping characters out from
// $search it seems only fair to modify it now so it will be displayed
// in the heading
This is nothing new.The safeString() function is in the utilityfunctions.php file.
It simply removes any nonalphanumeric characters from the input string via a regular
expression replacement. Because we have covered this topic before, we did not include it
here in the text.
The main reason that you need to validate input in this application is that you use the
customer’s input to create filenames in the cache.You could run into serious problems if
you allow customers to include .. or / in their input.
Next, you set up the customer’s shopping cart, if she does not already have one:
if(!isset($_SESSION['cart'])) {
session_register('cart');
$_SESSION['cart'] = array();
You still have a few tasks to perform before you can display the information in the top
information bar on the page (see Figure 33.1 for a reminder of what this looks like). A
glimpse of the shopping cart is shown in the top bar of every page. It is therefore important
that the cart variable is up to date before this information is displayed:
// tasks that need to be done before the top bar is shown
if($action == 'addtocart') {
addToCart($_SESSION['cart'], $ASIN, $mode);
}
if($action == 'deletefromcart') {
deleteFromCart($_SESSION['cart'], $ASIN);
}
if($action == 'emptycart') {
$_SESSION['cart'] = array();
Here, you add or delete items from the cart as necessary before displaying the cart.We
come back to these functions when we discuss the shopping cart and checking out. If
you want to look at them now, they are in the file cartfunctions.php.We are leaving
them aside for a minute because you need to understand the interface to Amazon first.
Next, you include the file topbar.php. This file simply contains HTML and
a style sheet and a single function call to the ShowSmallCart() function (from
cartfunctions.php). It displays the small shopping cart summary in the top-right
corner of the figures.We come back to this when we discuss the cart functions.