sorry ... that was me ...

change where the // comment mark is ... silly me ...
Code:
          $chk_cats = $_SESSION['cart']->in_cart_check('master_categories_id','11')  + $_SESSION['cart']->in_cart_check('master_categories_id','12');
//          echo 'shipping ' . $type . ' chk_cats: ' . $chk_cats . '<br>';