help with soapvar and xml list

I'm trying to create a request with a list. Here is what the request 
should be:

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Body>
    <OFSFAAByAirportPairPerHour xmlns="http://ws.oag.com">
      <SecurityToken>string</SecurityToken>
      <DepartureDateTime>string</DepartureDateTime>
      <DepAirportCode>string</DepAirportCode>
      <ArrAirportCode>string</ArrAirportCode>
      <CarrierCodeFilterList>
        <CarrierCode>string</CarrierCode>
        <CarrierCode>string</CarrierCode>
      </CarrierCodeFilterList>
      <ServiceTypeIndicator>short</ServiceTypeIndicator>
      <GMTLocalTimeIndicator>short</GMTLocalTimeIndicator>
      <IncludeCodeShareDisclosure>boolean</IncludeCodeShareDisclosure>
      <SchedStatusIndicator>short</SchedStatusIndicator>
      <DataSource>short</DataSource>
      <ResultXML>string</ResultXML>
    </OFSFAAByAirportPairPerHour>
  </soap:Body>
</soap:Envelope>

So I can get everything except the CarrierCodeFilterList right. How 
would I use SoapVar or something else to create that? Here is an excerpt 
of what I'm using for the rest:

$params->SecurityToken = new SoapVar($sectoken, XSD_STRING, 'string', 
"http://www.w3.org/2001/XMLSchema");
$params->DepartureDateTime = new SoapVar('2007-06-06', XSD_STRING, 
'string', "http://www.w3.org/2001/XMLSchema");
$params->DepAirportCode = new SoapVar('BOI', XSD_STRING, 'string', 
"http://www.w3.org/2001/XMLSchema");
$client = new SoapClient('file.wsdl');
$airresult = $client->OFSByAirportPairPerHour($air);
$airport = $airresult->OFSByAirportPairPerHourResult;

It gives me an error about the specified type was not recognized for the 
CarrierCodeFilterList so I can't even use __getLastRequest.

Thanks!

Sorry if I double posted. Not sure if I did.