I have created a function to handle a retrieve request using the ExactTarget API with PHP. The problem is that there's no documentation for using Complex Filter Parts in retrieve requests using the PHP version of the API. Here is my code. Please let me know if you spot any issues with why the ComplexFilterPart object is not working. Thanks!
$request = new ExactTarget_RetrieveRequest();
$request->ObjectType = 'ListSubscriber';
$request->Properties = array('ObjectID', 'SubscriberKey', 'CreatedDate', 'ModifiedDate', 'Client.ID', 'Client.PartnerClientKey', 'ListID', 'Status', 'UnsubscribedDate', 'ID');
$request->Filter = array();
$filterSubscriberKey = new ExactTarget_SimpleFilterPart();
$filterSubscriberKey->Property = 'SubscriberKey';
$filterSubscriberKey->SimpleOperator = ExactTarget_SimpleOperators::equals;
$filterSubscriberKey->Value = array($subscriberEmailAddress);
$filterListSubscriberStatus = new ExactTarget_SimpleFilterPart();
$filterListSubscriberStatus->Property = 'Status';
$filterListSubscriberStatus->SimpleOperator = ExactTarget_SimpleOperators::equals;
$filterListSubscriberStatus->Value = array('Active');
$filterGroup = new ExactTarget_ComplexFilterPart();
$filterGroup->LeftOperand = $filterSubscriberKey;
$filterGroup->LogicalOperator = ExactTarget_LogicalOperators::_AND;
$filterGroup->RightOperand = $filterListSubscriberStatus;
$request->Filter = new SoapVar($filterGroup, SOAP_ENC_OBJECT, 'ComplexFilterPart', 'http://exacttarget.com/wsdl/partnerAPI');
$requestMsg = new ExactTarget_RetrieveRequestMsg();
$requestMsg->RetrieveRequest = $request;
$results = $client->Retrieve($requestMsg);
$subscriberLists = $results->Results;