JavaScript
var req;
if(window.XMLHttpRequest)
req = new XMLHttpRequest();
else
req = new ActiveXObject('Microsoft.XMLHTTP');
req.onreadystatechange = function() {
if(req.readyState !== 4 || req.status !== 200)
return;
var data = eval('(' + req.responseText + ')');
alert(data.ID);
}
req.open('GET', 'demo.php', true);
req.send();
jQuery
$.getJSON('demo.php', function(data) {
alert(data.ID);
});