Hello, I am a php coder thats just breaking into ajax. I have used this code succesfully on many of my pages but i've come to a point where i need a little more

Code:
function loadUpdates()
{

if (window.XMLHttpRequest)
  {// code for IE7+, Firefox, Chrome, Opera, Safari
  xmlhttp=new XMLHttpRequest();
  }
else
  {// code for IE6, IE5
  xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
  }
  	//loading animation
	document.getElementById("updates").innerHTML="<image src=../../images/loading.gif></img>";

	
xmlhttp.onreadystatechange=function()
  {
  if (xmlhttp.readyState==4 && xmlhttp.status==200)
    {
    document.getElementById("updates").innerHTML=xmlhttp.responseText;
    }
	
	
  }
xmlhttp.open("GET","updates.php",true);
xmlhttp.send();
}
This code simply loads another page into a DIV. I'd like to know what or how to adjust this code to load my php page as there are new rows entered into the database. I briefly read about changing xmlhttp.open("GET","updates.php",true); to 'false' to make it asyncronous, a constant connection. But i'm unsure if this is true or the most efficient way to load data as it's entered into the DB.

Thanks~