从我的数据库加载谷歌地图标记 - Loading Google MAP Markers from my Database

我遵循了谷歌api教程一点一点地试图从外部数据库加载我的数据库标记，但没有成功。

https://developers.google.com/maps/articles/phpsqlajax_v3

地图正在加载，但没有标记显示，我已经使用以下版本来拉我的标记

   <?php  
$dom = new DOMDocument("1.0");
$node = $dom->createElement("markers");
$parnode = $dom->appendChild($node); 
require_once ('classes/DB.php');
$db = new DB();
$result = $db->query("SELECT * FROM markers");
header("Content-type: text/xml"); 
// Iterate through the rows, adding XML nodes for each
while ($row = $db->fetchData($result)){  
  // ADD TO XML DOCUMENT NODE  
  $node = $dom->createElement("marker");  
  $newnode = $parnode->appendChild($node);   
  $newnode->setAttribute("name",$row['name']);
  $newnode->setAttribute("address", $row['address']);  
  $newnode->setAttribute("lat", $row['lat']);  
  $newnode->setAttribute("lng", $row['lng']);  
  $newnode->setAttribute("type", $row['type']);
} 
echo $dom->saveXML();
?>

当我加载这个页面时，我在页面的源代码中得到了标记，但是当我加载页面时，我仍然看不到标记

    <!DOCTYPE html >
  <head>
    <meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
    <meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
    <title>PHP/MySQL & Google Maps Example</title>
    <script type="text/javascript" src="http://maps.googleapis.com/maps/api/js?sensor=false"></script>
    <script type="text/javascript">
    //<![CDATA[
    var customIcons = {
      restaurant: {
        icon: 'http://labs.google.com/ridefinder/images/mm_20_blue.png'
      },
      bar: {
        icon: 'http://labs.google.com/ridefinder/images/mm_20_red.png'
      }
    };
    function load() {
      var map = new google.maps.Map(document.getElementById("map"), {
        center: new google.maps.LatLng(47.6145, -122.3418),
        zoom: 13,
        mapTypeId: 'roadmap'
      });
      var infoWindow = new google.maps.InfoWindow;
      // Change this depending on the name of your PHP file
      downloadUrl("pointer_1.php", function(data) {
        var xml = data.responseXML;
        var markers = xml.documentElement.getElementsByTagName("marker");
        for (var i = 0; i < markers.length; i++) {
          var name = markers[i].getAttribute("name");
          var address = markers[i].getAttribute("address");
          var type = markers[i].getAttribute("type");
          var point = new google.maps.LatLng(
              parseFloat(markers[i].getAttribute("lat")),
              parseFloat(markers[i].getAttribute("lng")));
          var html = "<b>" + name + "</b> <br/>" + address;
          var icon = customIcons[type] || {};
          var marker = new google.maps.Marker({
            map: map,
            position: point,
            icon: icon.icon
          });
          bindInfoWindow(marker, map, infoWindow, html);
        }
      });
    }
    function bindInfoWindow(marker, map, infoWindow, html) {
      google.maps.event.addListener(marker, 'click', function() {
        infoWindow.setContent(html);
        infoWindow.open(map, 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);
    }
    function doNothing() {}
    //]]>
  </script>
  </head>
  <body oncreate="load()">
    <div id="map" style="width: 500px; height: 300px"></div>
  </body>
</html>

xml输出一旦看到源

<?xml version="1.0"?>
<markers>
    <marker name="Pan Africa Market" 
            address="1521 1st Ave, Seattle, WA" lat="47.608940" 
            lng="-122.340141" 
            type="restaurant"/>
    <marker name="Buddha Thai &amp; Bar" 
            address="2222 2nd Ave, Seattle, WA" 
            lat="47.613590" lng="-122.344391" 
            type="bar"/>
    <marker name="The Melting Pot" 
            address="14 Mercer St, Seattle, WA" lat="47.624561" 
            lng="-122.356445" 
            type="restaurant"/>
    <marker name="Ipanema Grill" 
            address="1225 1st Ave, Seattle, WA" 
            lat="47.606365" lng="-122.337654" 
            type="restaurant"/>
    <marker name="Sake House" 
            address="2230 1st Ave, Seattle, 
            WA" lat="47.612823" 
            lng="-122.345673" 
            type="bar"/>
    <marker name="Crab Pot" 
            address="1301 Alaskan Way, Seattle, WA" 
            lat="47.605961" 
            lng="-122.340363" 
            type="restaurant"/>
    <marker name="Mama's Mexican Kitchen" 
            address="2234 2nd Ave, Seattle, WA" 
            lat="47.613976" 
            lng="-122.345467" 
            type="bar"/>
    <marker name="Wingdome" 
            address="1416 E Olive Way, Seattle, WA" 
            lat="47.617214" 
            lng="-122.326584" 
            type="bar"/>
    <marker name="Piroshky Piroshky" 
            address="1908 Pike pl, Seattle, WA" 
            lat="47.610126" 
            lng="-122.342834" 
            type="restaurant"/>
</markers>

知道我可能做错了什么吗?

也许您忘记将标记分配给地图，就像这样:

marker.setMap(map);