Nusoap错误“WSDL文档中没有定义任何操作！”

Hi I'm getting an error:

no operations defined in the WSDL document!

I'm searching all possible ways that might answer my problem for almost a week but no luck I can't find it. I use nusoap library and here's my code:

<?php
include_once('lib/nusoap.php');
$username = 'xxxxx@username.com';
$password = 'xxxxxxx';

$endpoint = 'https://mail.xxxxxxxxx.com/ews/services.wsdl';
$wsdl = true;
$soapclient = new nusoap_client($endpoint, $wsdl);

 $xml = '<wsdl:definitions targetNamespace="http://schemas.microsoft.com/exchange/services/2006/messages">';
 $xml .= '<wsdl:message name="UploadItemsSoapIn">';
 $xml .= '<wsdl:part name="request" element="tns:UploadItems"/>';
 $xml .= '<wsdl:part name="Impersonation" element="t:ExchangeImpersonation"/>';
 $xml .= '<wsdl:part name="MailboxCulture" element="t:MailboxCulture"/>';
 $xml .= '<wsdl:part name="RequestVersion" element="t:RequestServerVersion"/>';
 $xml .= '</wsdl:message>';
 $xml .= '</wsdl:definitions>';

$operation = 'UploadItemsSoapIn';
$result = $soapclient->call($operation,$xml);

$soapclient->setCredentials($username, $password, 'ntlm');

if ($soapclient->fault) {
  echo '<h2>Fault (Expect - The request contains an invalid SOAP body)</h2><pre>'; print_r($result); echo '</pre>';
} else {
  $err = $soapclient->getError();
  if ($err) {
    echo '<h2>Error</h2><pre>' . $err . '</pre>';
  } else {
    echo '<h2>Result</h2><pre>'; print_r($result); echo '</pre>';
  }
}

and this is the view in services.wsdl link:

<wsdl:definitions targetNamespace="http://schemas.microsoft.com/exchange/services/2006/messages">
 <wsdl:types>
  <xs:schema>
   <xs:import namespace="http://schemas.microsoft.com/exchange/services/2006/messages" schemaLocation="messages.xsd"/>
   </xs:schema>
 </wsdl:types>

 <wsdl:message name="UploadItemsSoapIn">
   <wsdl:part name="request" element="tns:UploadItems"/>
   <wsdl:part name="Impersonation" element="t:ExchangeImpersonation"/>
   <wsdl:part name="MailboxCulture" element="t:MailboxCulture"/>
   <wsdl:part name="RequestVersion" element="t:RequestServerVersion"/>
  </wsdl:message>

 <wsdl:message name="UploadItemsSoapOut">
  <wsdl:part name="UploadItemsResult" element="tns:UploadItemsResponse"/>
  <wsdl:part name="ServerVersion" element="t:ServerVersionInfo"/>
 </wsdl:message>

Sorry I'm just a newbie in soap. All I want is just to run the basic function and just display email or names of the login user. Thanks in advance!