确切目标'不是defined"错误

我正在使用在http://help.exacttarget.com/en/technical_library/web_service_guide/api_starter_kits/上找到的确切目标PHP API入门工具包，并尝试使用示例代码进行连接。作为参考，下面是提供的示例代码:

<?php 
echo '<pre>';
require('../../00 Includes/exacttarget_soap_client.php');
<?php 
echo '<pre>';
require('../../00 Includes/exacttarget_soap_client.php');
$wsdl = 'https://webservice.s6.exacttarget.com/Service.asmx';
try{
         /* Create the Soap Client */
        $client = new ExactTargetSoapClient($wsdl, array('trace'=>1));
        /* Set username and password here */
        $client->username = '<ommitted>';
        $client->password = '<omitted>';
        $request = new ExactTarget_RetrieveRequest();
        $objectType= "Subscriber"; 
        $request->ObjectType= $objectType;
        $request->Properties = array("ID","PartnerKey","CreatedDate","Client.ID","Client.PartnerClientKey","EmailAddress","SubscriberKey","UnsubscribedDate","StatusSubscriberStatus");  
        // Filter retrieve on a particular email address
        $filter1 = new ExactTarget_SimpleFilterPart() ;
        $filter1->Property= "EmailAddress";
        $filter1->SimpleOperator=ExactTarget_SimpleOperators::equals;
        $filter1->Value=array("info@exacttarget.com");   //email address to filter on
        $request->Filter = new SoapVar($filter1, SOAP_ENC_OBJECT, 'SimpleFilterPart', "http://exacttarget.com/wsdl/partnerAPI"); 
        $requestMsg = new ExactTarget_RetrieveRequestMsg();
        $requestMsg->RetrieveRequest=$request;
        $results = $client->Retrieve($requestMsg);          
        /* Output the results */
        echo 'Results:';
        var_dump($results);

  } catch (SoapFault $e) {
    /* output the resulting SoapFault upon an error */
    var_dump($e);
}
/* Output the request and response */
print "Request: 'n".   $client->__getLastRequestHeaders() ."'n";
print "Request: 'n".
$client->__getLastRequest() ."'n";
print "Response: 'n".
$client->__getLastResponseHeaders()."'n";
print "Response: 'n".
$client->__getLastResponse()."'n";
echo '</pre>';
?>

当我运行这段代码时，我遇到了一个异常消息:

SOAP-ERROR: Parsing WSDL: Couldn't load from 'https://webservice.s6.exacttarget.com/Service.asmx' : Entity 'nbsp' not defined

我以前使用过确切的目标API，有两个奇怪的事情:

1. 错误发生在第10行，并且在SoapClient构造函数中触发，该构造函数由exacttarget_soap_client类继承。
2. 我已经分配了一个用户名，其中有一个空格。
3. 原来的API工具包使用wsdl url https://webservice.exacttarget.com/etframework.wsdl，它提供了一个"不正确的端点"错误。因此，我使用https://salesforce.stackexchange.com/questions/44614/request-was-made-to-the-incorrect-endpoint上列出的每个端点进行了尝试。使用任何一个端点，我得到实体未定义错误。

还有其他人遇到这个问题吗?