SOAP PHP值不能为null。 参数名称：source

I'm trying to call a function from this webservice:

http://www.zulutrade.com/WebServices/Performance.asmx?WSDL

I'm sending all the requested params but I'm getting this error: Value cannot be null. Parameter name: source I think it's a server issue, but maybe I need to change something in my code:

$client = new SoapClient('http://www.zulutrade.com/WebServices/Performance.asmx?WSDL',
                         array('location' => "http://www.zulutrade.com/WebServices/Performance.asmx",
                               'trace'=>1, 
                               "cache_wsdl" => 0));

$params = array
(
    'providerId' => 109206,
    'fromDateStr' => "1985-12-19",
    'toDateStr' => "2013-05-06",
    'validTrades' => true,
    'lotSize' => "Mini",
    'start' => 0,
    'length' => 20,
    'sortBy' => "buy",
    'sortAscending' => true
);

try
{
    $result =  $client->GetProviderTrades($params);
}
catch (SoapFault $fault)
{
    print_r($fault);
}

Any ideas? thanks

I tried with nusoap class and I get this error

HTTP Error: Couldn't open socket connection to server http://www.zulutrade.com:81/WebServices/Performance.asmx, Error (10060): A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond

So maybe it's a bug on their part

You set all vars except one. ArrayOfInt currencyIds; is not set.

struct GetProviderTrades {
 int providerId;
 ArrayOfInt currencyIds;
 string fromDateStr;
 string toDateStr;
 boolean validTrades;
 LotSize lotSize;
 int start;
 int length;
 string sortBy;
 boolean sortAscending;
}