How to display a loading message until the content is fully loaded - php

Question

I am using "http://www.w3schools.com/Php/php_ajax_database.asp" for displaying data from database on onchange of dropdown list. I have a huge amount of data in database. So it's taking time to load. Hence I would like to display a loading message somewhere in the page until the data display.
Code:
<script>
function showUser(str)
{
if (str=="")
{
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","getuser.php?q="+str,true);
xmlhttp.send();
}
</script>
<form>
<select name="users" onChange="showUser(this.value)" style="margin-left: -680px;margin-top: -10px;">
<option value="1">Current Projects</option>
<option value="2">All Projects</option>
</select>
</form>
</div></div>
<div id="txtHint"> /*Content*/ </div>
getuser.php:
Database queries to display data.

Answer 1

In my opinion it is easier to juse a javascribt library/framework like JQuery for Ajax requests or plain everything javascript. If you want to do it the old school way, that this should be able to help you out:
if(obj.readyState == 0)
{
document.getElementById('copy').innerHTML = "Sending Request...";
}
if(obj.readyState == 1)
{
document.getElementById('copy').innerHTML = "Loading Response...";
}
if(obj.readyState == 2)
{
document.getElementById('copy').innerHTML = "Response Loaded...";
}
if(obj.readyState == 3)
{
document.getElementById('copy').innerHTML = "Response Ready...";
}
if(obj.readyState == 4)
{
if(obj.status == 200)
{
return true;
}
else if(obj.status == 404)
{
// Add a custom message or redirect the user to another page
document.getElementById('copy').innerHTML = "File not found";
}
else
{
document.getElementById('copy').innerHTML = "There was a problem retrieving the XML.";
}
}

Answer 2

It's pretty easy actually, just put the message / image you want in the div, like that :
<div id="txtHint"> Loading... </div>
And when the data is loaded and JS :
document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
This will empty the div and replace with the Ajax content.
Actually, I think your code is already working.