How do I see the actual XML generated by PHP SOAP Client Class?

Use getLastRequest. It returns the XML sent in the last SOAP request.

echo "REQUEST:\n" . $SOAP->__getLastRequest() . "\n";

And remember, this method works only if the SoapClient object was created with the trace option set to TRUE. Therefore, when creating the object, use this code:

$SOAP = new SoapClient($WDSL, array('trace' => 1));

$SOAP = new SoapClient($WSDL, array('trace' => true));

$Response = $SOAP->DoRemoteFunction($Data);

echo "REQUEST:\n" . htmlentities($SOAP->__getLastRequest()) . "\n";

This will not only print the last request but also make the XML tags visible in the browser.

 was wrapping the response and thought that SoapClient was refusing to display the last request. A simple view:source corrected that and htmlspecialchars() made it all better.
                        				                   		

If you'd like to view the request without actually making a connection, you can override SoapClient's __doRequest method to return the XML:

class DummySoapClient extends SoapClient {
    function __construct($wsdl, $options) {
        parent::__construct($wsdl, $options);
    }
    function __doRequest($request, $location, $action, $version, $one_way = 0) {
        return $request;
    }
}
$SOAP = new DummySoapClient('http://example.com/?wsdl', array('trace' => true));
echo $SOAP->GetRequestDetail($params);

Extending Quinn's answer, you can also just log the request before you perform the request.

class SoapClientDebug extends SoapClient
{

public function __doRequest($request, $location, $action, $version, $one_way = 0)
{
    error_log("REQUEST:\n" .$request . "\n");
    error_log("LOCATION:\n" .$location . "\n");
    error_log("ACTION:\n" .$action . "\n");
    error_log("VERSION:\n" .$version . "\n");
    error_log("ONE WAY:\n" .$one_way . "\n");

    return parent::__doRequest($request, $location, $action, $version, $one_way);
}
}

You need to enable tracing when you create your SoapClient. Like so:

$SOAP = new SoapClient($WSDL, array('trace' => true));

$Data = array('Something'=>'Some String','SomeNumber'=>22); 

Then call the __getLastRequest method after you've made a service call to see the XML.

$Response = $SOAP->DoRemoteFunction($Data);
echo $SOAP->__getLastRequest();

This will output the request XML.

More reading: http://www.php.net/manual/en/soapclient.getlastrequest.php

if you are running the client locally, Fiddler is a great implementation agnostic way of looking at the messages on the wire.

If you are running it remotely then you could use something like Apache TCPMON Standalone or through eclipse*

*just linking to the first hit from Google

The problem with Quinn Comendant's answer, that $request from __doRequest() will then be processed by __call() and the user will see an array of parameters instead of real xml request. To prevent this, such workaround can be used:

class DummySoapClient extends SoapClient {
    function __construct($wsdl, $options) {
        parent::__construct($wsdl, $options);
    }

    function __doRequest($request, $location, $action, $version, $one_way = 0) {
        throw new Exception($request);
    }

    function __call($function_name, $arguments)
    {
        try {
            parent::__call($function_name, $arguments);
        } catch (Exception $e) {
            return $e->getMessage();
        }
    }
}

Option trace is not necessary here, because we do not call __getLastRequest() or other relevant functions.