Pass php variable to Ajax

[alicefreak]

Hello guys, I want to pass php variable to ajax. My whole script is working correctly.

var age = document.getElementById('$age').value;
queryString = "?age=" + age ;
ajaxRequest.open("GET", "ajax-example.php" + queryString, true);
ajaxRequest.send(null); 

. I know its wrong. Please help.

Thanks