<s:sequence>
    <s:any/>
</s:sequence>

请告诉我这是什么

<s:element name="CalculStudents">
    <s:complexTyPE>
        <s:sequence>
            <s:element minOccurs="0" maxOccurs="1" name="doc">
                <s:complexType mixed="true">
                    <s:sequence>
                        <s:any/>
                    </s:sequence>
                </s:complexType>
            </s:element>
        </s:sequence>
    </s:complexType>
</s:element>

使用PHP我在下面调用这个函数是我的代码

$client = new SOApClient("some.wsdl");
 $params = array("any"=>'');
 $result = $client->CalculStudents(array('doc'=>$params));

但这是一个错误

Exception Error! Server was unable to PRocess 
 request.Object reference not set to an instance of an object.

告诉我如何解决这个问题.这是一个PHP调用错误还是wsdl错了？