phpCAS::forceAuthentication PHP Method

    public static function forceAuthentication()
    {
        phpCAS::traceBegin();
        phpCAS::_validateClientExists();
        $auth = self::$_PHPCAS_CLIENT->forceAuthentication();
        // store where the authentication has been checked and the result
        self::$_PHPCAS_CLIENT->markAuthenticationCall($auth);
        /*      if (!$auth) {
                 phpCAS :: trace('user is not authenticated, redirecting to the CAS server');
                self::$_PHPCAS_CLIENT->forceAuthentication();
                } else {
                phpCAS :: trace('no need to authenticate (user `' . phpCAS :: getUser() . '\' is already authenticated)');
                }*/
        phpCAS::traceEnd();
        return $auth;
    }

function checkAndSetUserSession()
{
    // store session data
    if (!isset($_SESSION['user'])) {
        $_SESSION['user'] = null;
    }
    if (isset($_REQUEST['login']) or isset($_REQUEST['logout'])) {
        // initialize phpCAS
        phpCAS::client(CAS_VERSION_2_0, 'login.kth.se', 443, '');
        //phpCAS::proxy(CAS_VERSION_2_0,'login.kth.se',443,'');
        phpCAS::setNoCasServerValidation();
        // If you want the redirect back from the login server to enter your application by some
        // specfic URL rather than just back to the current request URI, call setFixedCallbackURL.
        //phpCAS::setFixedCallbackURL('http://xml.csc.kth.se/~wiiala/DM2517/project/php/index.php');
        // force CAS authentication
        phpCAS::forceAuthentication();
        // at this step, the user has been authenticated by the CAS server
        // and the user's login name can be read with phpCAS::getUser().
        $_SESSION['user'] = phpCAS::getUser();
        //Logga ut och redirecta till vår standardsida
        if (isset($_REQUEST['logout'])) {
            unset($_SESSION['user']);
            phpCAS::logoutWithRedirectService('http://kth.kribba.com/');
        }
    }
}