A SOAP Client

[sukishan]

A SOAP Client
Now I'll write a client for an existing SOAP server, so you can see it in action. I'll use XMethods' Barnes & Noble Price Quote server, which acts a lot like the example server, above. It takes an ISBN as input and returns price data from Barnes & Noble.

The client script will need to send a request containing an ISBN and then parse the response. In this script, I use the soapclient class, its constructor, and call, which handles making a request and parsing the response all in one. The only method available on the server is GetPrice, which takes only one parameter, a string called isbn. It returns a floating-point variable called return.

<?php
// include the SOAP classes
require_once('nusoap.php');
// define parameter array (ISBN number)
$param = array('isbn'=>'0385503954');
// define path to server application
$serverpath ='http://services.xmethods.net:80/soap/servlet/rpcrouter';
//define method namespace
$namespace="urn:xmethods-BNPriceCheck";
// create client object
$client = new soapclient($serverpath);
// make the call
$price = $client->call('getPrice',$param,$namespace);
// if a fault occurred, output error info
if (isset($fault)) {
        print "Error: ". $fault;
        }
else if ($price == -1) {
        print "The book is not in the database.";
} else {
        // otherwise output the result
        print "The price of book number ". $param[isbn] ." is $". $price;
        }
// kill object
unset($client);
?>The soapclient constructor takes a server URL as its argument. Having thus initialized the server object, I pass to the call method the name of the function I want (getPrice), the necessary parameters (the array containing the ISBN string to look up), and the required method namespace: urn:xmethods-BNPriceCheck.

The parameters for soapclient's call method are: function name, parameter array, and three optional ones: namespace, SOAPAction, and an array of headers. The definition for the server will specify which, if any, of the optional parameters are necessary. The Barnes & Noble Price Quote server requires a method namespace definition (urn:xmethods-BNPriceCheck) but no SOAPAction or SOAP headers. Information about what this server offers and what it requires was gleaned from the server's listing on XMethods' index of SOAP servers. (This particular server happens to be hosted by XMethods, but the index lists a wide variety of servers, regardless of host.)

The call method of the client performs the SOAP transaction and returns the content of the server's response to the $price variable. The script checks for the presence of $fault, which the server returns if there was an error in the transaction. If the $fault variable is set, the script outputs the error information. If there isn't an error, it checks to see if the price returned is -1, which indicates that the requested book was not found. Otherwise, the price data is printed.