Set Session Timeout

session_start();

// set timeout period in seconds
$inactive = 600;

// check to see if $_SESSION['timeout'] is set
if(isset($_SESSION['timeout']) ) {
        $session_life = time() - $_SESSION['timeout'];
        if($session_life > $inactive)
        { session_destroy(); header("Location: logout.php"); }
}
$_SESSION['timeout'] = time();