Creating Web Services with PHP and SOAP, Part 2

The terminology has changed slightly in naming some of the elements in the WSDL 2.0 specification. portType, for example, has changed its name to Interface. Since support for WSDL 2.0 is weak, I’ve chosen to go over version 1.1 which is more widely used.

Building a WSDL File

WSDL files can be cumbersome to write by hand as they must contain specific tags and are usually quite long. The nice thing about using NuSOAP is that it can create a WSDL file for you! Let’s modify the SOAP server we made in the first article to accommodate this.

Open productlist.php and change it to reflect the code below:

<?php
require_once "nusoap.php";
function getProd($category) {
    if ($category == "books") {
        return join(",", array(
            "The WordPress Anthology",
            "PHP Master: Write Cutting Edge Code",
            "Build Your Own Website the Right Way"));
    }
    else {
        return "No products listed under that category";
    }
}
$server = new soap_server();
$server->configureWSDL("productlist", "urn:productlist");
$server->register("getProd",
    array("category" => "xsd:string"),
    array("return" => "xsd:string"),
    "urn:productlist",
    "urn:productlist#getProd",
    "rpc",
    "encoded",
    "Get a listing of products by category");
$server->service($HTTP_RAW_POST_DATA);

The second change adds additional arguments to the register() method. Breaking it down:

• getProd is the function name
• array("category" => "xsd:string") defines the input argument to getProd and its data type
• array("return" => "xsd:string") defines the function’s return value and its data type
• urn:productlist defines the namespace
• urn:productlist#getProd defines the SOAP action
• rpc defines the type of call (this could be either rpc or document)
• encoded defines the value for the use attribute (encoded or literal could be used)
• The last parameter is a documentation string that describes what the getProd function does

Now point your browser to http://yourwebroot/productlist.php?wsdl and you’ll see the brand new WSDL file created for you. Go ahead and copy that source and save it as it’s own file called products.wsdl and place it in you web directory.

Consuming WSDL Files with the Client

We’ve modified the SOAP server to generate a WSDL file, so now lets modify the SOAP client to consume it. Open up productlistclient.php created in the previous article and simply change the line that initiates the client from this:

$client = new nusoap_client("http://localhost/nusoap/productlist.php");

$client = new nusoap_client("products.wsdl", true);

Summary

In part 2 of this series on creating web services with PHP and SOAP, we went over the importance of using WSDL files for optimum interoperability. We talked about the different elements that make up a WSDL file and their definitions, and then I showed you how to quickly and easily create your own WSDL files with the NuSOAP library. Finally, we modified our SOAP server and client to demonstrate how to use WSDL in your applications.

As you can probably guess, I’ve just barely scraped the surface of what SOAP can do for you, but with these new tools you can provide an easy and well-accepted way of exposing web services to your users.

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