if (isset($_GET['a']) )  {


    $aktivan_grad = $_GET['a'];

    if ($aktivan_grad == ns) {

      $_SESSION['grad1'] = 'active';
      $_SESSION['grad2'] = '';
      $_SESSION['grad3'] = '';

      $_SESSION['grb1'] = 'active-grb';
      $_SESSION['grb2'] = '';
      $_SESSION['grb3'] = '';


    } elseif ($aktivan_grad == sa) {

      $_SESSION['grad2'] = 'active';
      $_SESSION['grad1'] = '';
      $_SESSION['grad3'] = '';

      $_SESSION['grb1'] = '';
      $_SESSION['grb2'] = 'active-grb';
      $_SESSION['grb3'] = '';

    } elseif ($aktivan_grad == ni) {

      $_SESSION['grad3'] = 'active';
      $_SESSION['grad1'] = '';
      $_SESSION['grad2'] = '';

      $_SESSION['grb1'] = '';
      $_SESSION['grb2'] = '';
      $_SESSION['grb3'] = 'active-grb';
    }


 }

?>