Using Ajax in netbeans with Javascript

I am currently following the W3 school tutorial in the following link http://www.w3schools.com/ajax/ajax_aspphp.asp. I have the code below that I am using but I can't get any suggestions to appear in the output like shown in example. I have used firebug and it returns the correct php File that I have but doesn't execute it onto the webpage. (Using it in netbeans)

<script>
function showHint(str)
{
var xmlhttp;
if (str.length==0)
 { 
  document.getElementById("txtHint").innerHTML="";
   return;
 }
 if (window.XMLHttpRequest)
    {// code for IE7+, Firefox, Chrome, Opera, Safari
   xmlhttp=new XMLHttpRequest();
   }
  else
  {// code for IE6, IE5
   xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
   }
   xmlhttp.onreadystatechange=function()
 {
  if (xmlhttp.readyState==4 && xmlhttp.status==200)
  {
  document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
  }
}
 xmlhttp.open("GET","gethint.php?q="+str,true);
 xmlhttp.send();
 </script>

 <h3>Start typing a name in the input field below:</h3>
 <form action=""> 
 First name: <input type="text" id="txt1" onkeyup="showHint(this.value)" />
 </form>
 <p>Suggestions: <span id="txtHint"></span></p> 
  }