var req;

function navigate(month,year) {
	var url = 'includes_php/calendar.php?month='+month+'&year='+year;
	
	if(window.XMLHttpRequest) {
		req = new XMLHttpRequest();
	} else if(window.ActiveXObject) {
		req = new ActiveXObject('Microsoft.XMLHTTP');
	}
	
	req.open('GET', url, true);
	req.setRequestHeader('X-Requested-With','XMLHttpRequest');
	req.setRequestHeader('If-Modified-Since','Wed, 15 Nov 1995 00:00:00 GMT');
	req.onreadystatechange = callback;
	req.send(null);
}

function callback() {
	if(req.readyState == 4) {
		if(req.status == 200) {
			response = req.responseText;
			if(document.getElementById('calendar')) {
				document.getElementById('calendar').innerHTML = response;
			}
		}
	}
}