session_start();

if ( isset($_SESSION['ip']) ) {
	if ( $_SESSION['ip'] != $_SERVER['REMOTE_ADDR'] ) {
		session_destroy(); session_start(); session_regenerate_id(); 
	}

} else {
	$_SESSION['ip'] = $_SERVER['REMOTE_ADDR'];
}


if ( isset($_GET['logout']) ) { 
	session_destroy(); session_start(); session_regenerate_id(); 
}