xmlHttp对象参考

var xmlhttp=null;
function PostOrder(xmldoc)
{
  var xmlhttp = new ActiveXObject("Msxml2.XMLHTTP.5.0");
  xmlhttp.Open("POST", "http://myserver/orders/processorder.asp", false);
  xmlhttp.onreadystatechange= HandleStateChange;
  xmlhttp.Send(xmldoc);
  myButton.disabled = true;
}
function HandleStateChange()
{
  if (xmlhttp.readyState == 4)
  {
    myButton.disabled = false;
    alert("Result = " + xmlhttp.responseXML.xml);
  }
}