XMLhttprequest - can't change states

[infamous_Q]

Ok, I don't know what I'm doing wrong here. I've written some script that is using javascript to send information to a MySQL db through a php page, and receive as well. Now, here's the kicker: I can send things fine, but I cannot receive anything, and it seems the request doesn't change it's state. So in order to trouble shoot I've set up a script that will pop up an alert message box every time the request's state changes, but it never gets passed 1. My code is below (it's snipped a bit, and I only included the non-working code).

 

function getInf()
{
xmlHttp=GetXmlHttpObject()
if (xmlHttp==null)
{
alert ("Your browswer doesn't support XML");
return;
}

var idinf="3"; 
//this number doesn't even matter really for troubleshooting
var url="get_inf.php?id=" + idinf;

xmlHttp.open("GET",url,true);

xmlHttp.onreadystatechange(checkData());
xmlHttp.send(idinf);

}

function checkData()
{
alert(xmlHttp.readyState);
}

 

Can anybody help me out?