Problem using JQuery XML and PHP

Problem using JQuery XML and PHP

So i have an HTML page which contains this script:

<script type="text/javascript">
          $(document).ready(function(){
            $.ajax({
                    type: "GET",
                    url: "http://meteo.uniparthenope.it/prods/timeseries._dev.php?region=ca001&when=now",
                    dataType: "xml",
                    success: function(xml) {
                        $(xml).find("time").each(function()
                        {
                            $("#output").append($(this).attr("date") + "<br />");
                        });
                    }
              });
          });
      </script>

This script doesn't work! If i copy the content given by the url in an XML File, the script works.
Am I doing right?
The html file isn't on the same machine of the php page.
I validated the response given by the url above through the wc3 online tools.
Using firebug to debug the script, i can read that the response is empty.
I don't know other details to give.