You almost for sure will need to wrap a try/catch block around your SOAP call in order to use these to debug something that's not working.
Otherwise, PHP throws a fatal error before you can execute this function.
For example:
<?php
$soapClient = new SoapClient($url);
echo htmlentities($soapClient->__getFunctions());
try {
$results = $soapClient->someFunction(...);
}
catch (SoapFault $soapFault) {
var_dump($soapFault);
echo "Request :<br>", htmlentities($soapClient->__getLastRequest()), "<br>";
echo "Response :<br>", htmlentities($soapClient->__getLastResponse()), "<br>";
}
?>
Without try/catch, your just get the Fatal Error and PHP commits suicide before you can call __getLastRequest/__getLastResponse
