XMLHttpRequestObject.responseText returns correct value on ALERT() but...

XMLHttpRequestObject.responseText returns correct value when i do alert(XMLHttpRequestObject.responseText); see line

var fnWhenDone = function (XMLHttpRequestObject) { alert(XMLHttpRequestObject.responseText); };

PHP:

But problem is that i want to save it down to a variable... so i try to change it into

var fnWhenDone = function (XMLHttpRequestObject) { varTest = XMLHttpRequestObject.responseText; };

PHP:

When i try to alert varTest later i get "Undifined"... im pretty new to javascript and have been stuck for hours

var myConn = new XHConn();

if (!myConn) { alert("XMLHTTP not available. Try a newer/better browser."); }

var fnWhenDone = function (XMLHttpRequestObject) { alert(XMLHttpRequestObject.responseText); };

myConn.connect("validateSearch.php", "POST", "foo=bar&baz=qux", fnWhenDone);


function XHConn()
{
  var xmlhttp, bComplete = false;
  try { xmlhttp = new ActiveXObject("Msxml2.XMLHTTP"); }
  catch (e) { try { xmlhttp = new ActiveXObject("Microsoft.XMLHTTP"); }
  catch (e) { try { xmlhttp = new XMLHttpRequest(); }
  catch (e) { xmlhttp = false; }}}
  if (!xmlhttp) return null;
  this.connect = function(sURL, sMethod, sVars, fnDone)
  {
    if (!xmlhttp) return false;
    bComplete = false;
    sMethod = sMethod.toUpperCase();
    try {
      if (sMethod == "GET")
      {
        xmlhttp.open(sMethod, sURL+"?"+sVars, true);
        sVars = "";
      }
      else
      {
        xmlhttp.open(sMethod, sURL, true);
        xmlhttp.setRequestHeader("Method", "POST "+sURL+" HTTP/1.1");
        xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
      }
      xmlhttp.onreadystatechange = function(){
        if (xmlhttp.readyState == 4 && !bComplete)
        {
          bComplete = true;
          fnDone(xmlhttp);
        }};
      xmlhttp.send(sVars);
    }
    catch(z) { return false; }
    return true;
  };
  return this;
}

PHP: