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!