怎么让soap server 返回一个xml文档？

小树叶子

想用soap做一个简单的小东西玩玩。返回的是段xml代码，运行时但是老是出错，请高手指点一下。
错误报告是：


Fatal error: Uncaught SoapFault exception: [Client] looks like we got no XML document in E:\Website\test\soap\SoapClient.php:7 Stack trace: #0 [internal function]: SoapClient->__call('GetAddressByIP', Array) #1 E:\Website\test\soap\SoapClient.php(7): SoapClient->GetAddressByIP('220.174.214.50') #2 {main} thrown in E:\Website\test\soap\SoapClient.php on line 7


至于soap server文件，<?前后没有空格或空白行，编码没有中文。wsdl是用zde生成的，PHP版本是最新的。

wsdl : http://liusha.org/labs/soap/ip.wsdl
soap serverfile http://liusha.org/labs/soap/ipserver.php


soap client code:

$ws = 'http://liusha.org/labs/soap/ip.wsdl';
$soapclient = new SoapClient($ws);
//print_r($soapclient->__getFunctions());
$soapclient->GetAddressByIP('220.174.214.50');