A quick example of how easy it is to consume web services with PHP, using PEAR::SOAP and WSDL, as there isn’t much material around.

Picking a web service at random described by this WSDL document http://wavendon.dsdata.co.uk/axis/services/CarRentalQuotes?wsdl, here’s how to consume it with PEAR::SOAP.

First check out the proxy code generated from the WSDL document so you understand the available methods (note this a good way to mentally “reverse engineer” what WSDL actually says);

<?php
require_once('SOAP/Client.php'); 
$wsdl=new SOAP_WSDL(
    'http://wavendon.dsdata.co.uk/axis/services/CarRentalQuotes?wsdl');

// Look at the generated code... 
echo ( $wsdl->generateProxyCode() ); 
?>

This will display something like;

class WebService_CarRentalQuotesService_CarRentalQuotes extends SOAP_Client {
 
    function WebService_CarRentalQuotesService_CarRentalQuotes() {
        $this->SOAP_Client(
            "http://wavendon.dsdata.co.uk/axis/services/CarRentalQuotes", 0);
    }
 
    function getQuotes($carType, $country, $currency, $pickupDate, 
                             $pickupLocation, $returnDate, $returnLocation) {
        // SOAP Stuff here
    }
 
    function getCountries() {
        // SOAP Stuff here
    }
 
    function getLocations($country) {
        // SOAP Stuff here
    }
 
    function getCurrencies() {
        // SOAP Stuff here
    }
 
    function getCarTypes() {
        // SOAP Stuff here
    }
}

Now you know what the methods are and their parameters.

Note I’ve chopped down the above code to make it readable but make sure you try it yourself - basically the generated code makes use of the underlying SOAP_Client class - if you’ve had any experience of XML-RPC, you had to hand code this stuff - this is the big step forward WSDL brings.

You could then apply eval() to the above code then instantiate an object by PEAR::SOAP already provides the method getProxy() which does it for you;

<?php
require_once('SOAP/Client.php'); 
$wsdl=new SOAP_WSDL(
    'http://wavendon.dsdata.co.uk/axis/services/CarRentalQuotes?wsdl');

// Create an object directly from the proxy code
$carRentalQuotes=$wsdl->getProxy(); 

$countries=$carRentalQuotes->getCountries();

print_r ( $countries ); 
?>

You get back a list of countries from the remote SOAP server, which you could then feed back into the getLocations() method. Note bad for four lines of code.

Note: at some point people will start implement WSCI (Web Service Choreography InterfaceXMethods - watch out for those described as “Document Literal” - these are a bit more tricky - reasons explained in brief here.

I’ll look at building SOAP servers some other time with PEAR::SOAP (it’s also easy - credit to the authors). The harder part is writing WSDL document to describe your service - basically you need to do it manually. Explaining WSDL is more than a quick article but some time...

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