php访问wcf对象传参服务

以下是wcf服务接口
[OperationContract]
List<UserInfo> GetInfoByParam(UserInfo userInfo);
现在php中要访问些接口
$soap = new SoapClient ( "http://localhost:4625/Service1.svc?wsdl" );
$result = $soap->GetInfoByParam ( array (
'userInfo' => array (
'Age' => 18
)
) );

下划线加粗了,你懂滴