Accessing IPAM via SOAP

Hi guys. Does anyone have any example code for accessing IPAM via SOAP and PHP? Here's what I have so far:

$sc = new SoapClient("https://server:17778/SolarWinds/InformationService?wsdl", array("login" => "xxx", "password" => "xxx", "trace" => "1"));
$q = 'SELECT IpNodeId FROM IPAM.IPNode';
$qo = array();
print_r($sc->Query($q, $qo));

Here's the error I get:

PHP Fatal error:  Uncaught SoapFault exception: [a:InternalServiceFault] End element 'Body' from namespace 'http://schemas.xmlsoap.org/soap/envelope/' expected. Found element 'param1' from namespace ''. Line 2, position 229. in D:\Documents\port\iprepo.php:9
Stack trace:
#0 D:\Documents\port\iprepo.php(9): SoapClient->__call('Query', Array)
#1 D:\Documents\port\iprepo.php(9): SoapClient->Query('SELECT IpNodeId...', Array)
#2 {main}
  thrown in D:\Documents\port\iprepo.php on line 9