When calling over SOAP to a .NET application, you may end up with an object as a result instead of a simple type, even if you're just grabbing a simple type (like a boolean result). Use a property accessor to get the actual result, like this:
<?php
$client = new SoapClient("http://server/myservice.asmx?WSDL");
$objectresult = $client->MyMethod($param1, $param2);
$simpleresult = $objectresult->MyMethodResult;
?>
Note that .NET seems to name the result MethodNameResult for method MethodName.