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

824 Chapter 33 Connecting to Web Services with XML and SOAP
The DEVTAG constant holds the value of the developer token Amazon gives you when
you sign up.You need to change this value to your own developer token; otherwise, the
application will not work.You can sign up for a tag at http://aws.amazon.com.
Now let’s look back at index.php. It contains some preliminaries and then the main
event loop.You begin by extracting any incoming variables from the $_REQUEST superglobal
that came via GET or POST.You then set up some default values for some standard
global variables that determine what will be displayed later, as follows:
// default values for global variables
if($mode=='') {
$mode = 'Books'; // No other modes have been tested
}
if($browseNode=='') {
$browseNode = 53; //53 is bestselling non-fiction books
}
if($page=='') {
$page = 1; // First Page - there are 10 items per page
You set the mode variable to Books. Amazon supports many other modes (types of products),
but for this application, you just need to worry about books. Modifying the code
in this chapter to deal with other categories should not be too hard.The first step in this
expansion would be to reset $mode.You would need to check the Amazon documentation
to see what other attributes are returned for nonbook products and remove bookspecific
language from the user interface.
The browseNode variable specifies what category of books you would like displayed.
This variable may be set if the user has clicked through one of the Selected Categories
links. If it is not set—for example, when the user first enters the site—you will set it to
53. Amazon’s browse nodes are simply integers that identify a category.The value 53 represents
the category Non-Fiction Books, which seems as good a node as any other to
display on the initial front page given that some of the best generic categories (such as
Best Sellers) are not available as browse nodes.
The page variable tells Amazon which subset of the results you would like displayed
within a given category. Page 1 contains results 1–10, page 2 has results 11–20, and so
on. Amazon sets the number of items on a page, so you do not have control over this
number.You could, of course, display two or more Amazon “pages” of data on one of
your pages, but 10 is both a reasonable figure and the path of least resistance.
Next, you need to tidy up any input data you have received, whether through the
search box or via GET or POST parameters:
//validate/strip input
if(!eregi('^[A-Z0-9]+$', $ASIN)) {
// ASINS must be alpha-numeric
$ASIN ='';
}