function doMap()
{
    var map = new GMap2(document.getElementById("map"));
    map.addControl(new GLargeMapControl());
    map.addControl(new GMapTypeControl());
    map.setCenter(new GLatLng(0, 0), 1);

    GDownloadUrl("geo.php", function(data, responseCode) 
      {            
         var xml = GXml.parse(data);
         var photos = xml.documentElement.getElementsByTagName("photo");
         
        for (var i = 0; i < photos.length; i++) 
        { 
            var id = photos[i].getAttribute("id");
            var latitude = parseFloat(photos[i].getAttribute("latitude"));
            var longitude = parseFloat(photos[i].getAttribute("longitude"));
            var point = new GLatLng(latitude, longitude);
            var marker = createMarker(point, id);
    
            map.addOverlay(marker);
        }
      });
}


function createMarker(point, id)
{
    var marker = new GMarker(point);

    GEvent.addListener(marker, "click", function() 
    {
           marker.openInfoWindowHtml("<p>Photo Id: " + id + "</p>");
    });
        
    return marker;
}