function getWindowSize(phpSessionWindowWidth, phpSessionWindowHeight) {
	if (phpSessionWindowWidth != document.documentElement.clientWidth || phpSessionWindowHeight != document.documentElement.clientHeight) {
		var xhr;
		try { xhr = new XMLHttpRequest(); }
		catch (e) {
			xhr = new ActiveXObject(Microsoft.XMLHTTP);
		}  
		
		xhr.open('POST', 'php/util/windowSize.php', true);
		xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
		xhr.send('window_width=' + document.documentElement.clientWidth + '&window_height=' + document.documentElement.clientHeight);
	}
}