Php google maps js v3 xml为空

当我运行XML时，我试图检索XML并将其放入var标记中

var markers = xml.documentElement.getElementsByTagName("marker");

我得到一个错误，说XML为null，这是我在运行生成XML的文件时得到的XML

This XML file does not appear to have any style information associated with it. The document tree is shown below.
  <markers>
 <marker name="funtimes" address="5451 Forest Cove Lane" lat="34.1519" lng="-118.774717" type="Basketball" desc="going to play fun times with fun people" date="2012-12-29" time="23:00:00" eventcap="4" eventcur="10" eventid="1" admin="true"/>
 <marker name="Event test" address="1231 fake st" lat="34.1517" lng="-118.77234" type="Cycling" desc="just a description" date="2013-01-31" time="12:00:00" eventcap="10" eventcur="4" eventid="2" admin="true"/>
 <marker name="Event test 2" address="1231 fake st" lat="34.1512" lng="-118.77421" type="Football" desc="just a description 2" date="2013-01-31" time="12:00:00" eventcap="10" eventcur="3" eventid="3" admin="true"/>
 <marker name="funtimes" address="5451 Forest Cove Lane" lat="34.1519" lng="-118.774717" type="Basketball" desc="going to play fun times with fun people" date="2012-12-29" time="23:00:00" eventcap="4" eventcur="10" eventid="1" admin="false"/>    
 <marker name="Event test" address="1231 fake st" lat="34.1517" lng="-118.77234" type="Cycling" desc="just a description" date="2013-01-31" time="12:00:00" eventcap="10" eventcur="4" eventid="2" admin="false"/>
 <marker name="Event test 2" address="1231 fake st" lat="34.1512" lng="-118.77421" type="Football" desc="just a description 2" date="2013-01-31" time="12:00:00" eventcap="10" eventcur="3" eventid="3" admin="false"/>
 <marker name="Event test 3" address="2142 fake st" lat="34.1602" lng="-118.77789" type="Football" desc="just a description 3" date="2013-01-28" time="13:00:00" eventcap="8" eventcur="2" eventid="4" admin="false"/>
 </markers>

我已使用生成的XML从运行您的代码，没有错误。如果在我的文件中删除了行

标题（“内容类型：text/xml”）

，我会得到错误

未捕获类型错误：无法读取null的属性“documentElement”

，这表明您没有发送标题。记住，在发送任何实际输出之前，必须调用header（），可以是通过普通HTML标记、文件中的空行，也可以是通过PHP

试一试

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他的问题是缺少标题（“内容类型：text/xml”）；我的文件中有这样一个文件，它使xml成为可能的副本。你能在浏览器中打开xml吗？你在哪个浏览器中发现这个错误？我可以在firefox中打开xml，我在最初的问题中公布了结果。错误也出现在firefox中

downloadUrl("mapXML2.php", function(data) {
var xml = data.responseXML;
var markers = xml.documentElement.getElementsByTagName("marker");

 function downloadUrl(url, callback) {
      var request = window.ActiveXObject ?
      new ActiveXObject('Microsoft.XMLHTTP') :
      new XMLHttpRequest;

  request.onreadystatechange = function() {
    if (request.readyState == 4) {
      request.onreadystatechange = doNothing;
      callback(request, request.status);
    }
  };

  request.open('GET', url, true);
  request.send(null);
}

header("Content-type: text/xml");
// Start XML file, create parent node
$dom = new DOMDocument("1.0");
$node = $dom->createElement("markers");
$parnode = $dom->appendChild($node);
//Connect to database