CAS_Client::renewAuthentication PHP Method

    public function renewAuthentication()
    {
        phpCAS::traceBegin();
        // Either way, the user is authenticated by CAS
        if (isset($_SESSION['phpCAS']['auth_checked'])) {
            unset($_SESSION['phpCAS']['auth_checked']);
        }
        if ($this->isAuthenticated(true)) {
            phpCAS::trace('user already authenticated');
            $res = true;
        } else {
            $this->redirectToCas(false, true);
            // never reached
            $res = false;
        }
        phpCAS::traceEnd();
        return $res;
    }

 /**
  * This method is called to renew the authentication.
  *
  * @return void
  **/
 public static function renewAuthentication()
 {
     phpCAS::traceBegin();
     phpCAS::_validateClientExists();
     $auth = self::$_PHPCAS_CLIENT->renewAuthentication();
     // store where the authentication has been checked and the result
     self::$_PHPCAS_CLIENT->markAuthenticationCall($auth);
     //self::$_PHPCAS_CLIENT->renewAuthentication();
     phpCAS::traceEnd();
 }