php中，如何通过soap传递两个参数，（ms-security下）

$xml = '

            <wsse:Security xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">

            <wsse:UsernameToken>

            <wsse:Username>admin</wsse:Username>

            <wsse:Password>PasswordText</wsse:Password>

            </wsse:UsernameToken>

            </wsse:Security>';



        $header = new SoapHeader('http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd', 'CallbackHandler', new SoapVar($xml, XSD_ANYXML), TRUE);



        $this->client = new SoapClient($wsdl);

        $this->client->__setSoapHeaders(array($header));



        $userInfo = turnObjectToArray($this->client->__call('checkUser', array('username' => array('username' => 'username', 'password' => 'password'))));

一运行上述代码，就提示出错

SoapFault exception: [soap:Server] Fault occurred while processing. in 

后来连调时，对方看了下log，显示就把username传过去了，password没传过去


传递一个参数时对方是可以接收到的

$info = turnObjectToArray($this->client->__call('getClasses', array('gradeId' => array('gradeId' => $data['id']))));

怎么传递两个参数啊？？？
------解决方案--------------------
注意大小写 ！