Pro PHP- Patterns, Frameworks, Testing and More

CHAPTER 19 ■ INTRODUCTION TO WEB SERVICES WITH SOAP^295

A Real-World Example

Now that you know the theory of web services, let’s look at an example of one of the most

su cc e s sf u l a nd w i del y u sed w eb ser v i ce A PIs o n t h e W e b, A m az o n W eb Ser vi c es. Us i ng th i s A PI,

you can get a ton of useful information.

For this example, you will try to find a list of books that have Pro PHP in the title or that are

published by Apress. To start, most web services require some sort of key that controls access

and that enforces some basic requirements, such as how many queries you use on a daily basis.

There’s no cost to get this key, but you will need to sign up for one at http://aws.amazon.com.

Once you’ve signed up, you will receive an e-mail confirming your subscription. At the end of

that e-mail will be a link to get your access key, which you should follow; you will need this key

shortly.

The URL for the WSDL for the Amazon Web Services API is currently http://

webservices.amazon.com/AWSECommerceService/AWSECommerceService.wsdl, and the file is

immense. You’re going to use only a very small subset of this WSDL, specifically the ItemSearch

operation. This method has some nested parameters. First, the Amazon Web Services request

requires the parameter AWSAccessKeyId to be passed along with another parameter named

Request. Request is an associative array of data and can contain many optional keys, which are

well documented on the Amazon Web Services site. For this example, you will search for this book

by Title and Publisher, using the SearchIndex 'Books' and asking for a small ResponseGroup back

from the server.

So without further introduction, Listing 19-8 demonstrates an Amazon SOAP request.

Listing 19-8. Finding Book Information Using the Amazon Web Services API

<?php

$wsdl = "http://webservices.amazon.com/AWSECommerceService/AWSECommerceService ➥

.wsdl";

$client = new SoapClient($wsdl);

$namedParameters = array(

'AWSAccessKeyId' => 'YOUR_ACCESS_KEY',

'Request' => array(

'Title' => 'Pro PHP',

'SearchIndex' => 'Books',

'ResponseGroup' => 'Small',

'Publisher' => 'Apress'

)

);

$response = $client->ItemSearch($namedParameters);

var_dump($response);

In this example, you set the WSDL file to the WSDL provided by the Amazon Web Services

and initialize a SoapClient. You create an array following the parameter format defined by the

WSDL and the API documentation, and pass along your access key plus an array of request

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