“无效的XML”错误提示？

我通过Ajax将一些XML从PHP返回到Javascript，但得到“无效的XML”错误提示。返回的XML如下所示：

<response>
<song>tdb2009-01-29s2s06</song>
<song>tdb2009-01-29s1s02</song>
</response>

解析它的javascript如下所示：

 function u_handleServerResponse(){  
   //pull xml from xml response  
   var xmlResponse = xmlHttp.responseXML;

   //check to see if xml was pulled
   if(!xmlResponse || !xmlResponse.documentElement){
     throw("Invalid XML Structure:
" + xmlHttp.responseText);
   }

   //this is for catching errors with firefox
   var rootNodeName = xmlResponse.documentElement.nodeName;

   //check for errors
   if(rootNodeName == "parsererror"){
     throw("Invalid XML Strucutre");
   }

   //get the root
   xmlRoot = xmlResponse.documentElement;

   var songArray = xmlRoot.getElementsByTagName("song");

  for(var i = 0; i < songArray.length; i++){   
   etc., etc...

得到的错误如下：

Error reading the response: Invalid XML Strucutre

你觉得这是对的吗？XML本身是错的还是加载错了？我们非常感谢所有的帮助。

You may need to include an xml header...

<?xml version="1.0" ?> 

In addition to the XML header pointed out by rikh, you may need to declare the Content-Type header as text/xml for the responseXML to be correctly populated.

If you still have problems take a look at this article:
https://web.archive.org/web/1/http://articles.techrepublic%2ecom%2ecom/5100-10878_11-6141415.html

Regards,
Bruno