NuSoap Webservice出错

Question

-------------------------------要求提供此信息的网络服务---------- ----------------------

<s:element name="PREPO0001">
<s:complexType>
<s:sequence>
<s:element minOccurs="0" maxOccurs="1" name="p1" type="s:string"/>
<s:element minOccurs="0" maxOccurs="1" name="p2" type="s:string"/>
</s:sequence>
</s:complexType>
</s:element>

-------------------------------通过Webservice Codeigniter发送------------ --------------------

$this->nusoap_client = new nusoap_client("web-service link",'wsdl');
webservice_request= array('p1'=> $orden, 'p2' => $placa);
$row = $this->nusoap_client->call('PREPO0001',$webservice_request);

获得＆＃34;错误＆＃34;来自WS的消息有什么想法？

来自WS的Erro： {＆＃34; PREPO0001Result＆＃34;：＆＃34; ERROR＆＃34;}