- * @param string $output Passed by reference. Used to append additional content.
- * @param int $depth Depth of category. Used for tab indentation.
- * @param array $args An array of arguments. Will only append content if style argument value is 'list'.
- * @see wp_list_categories()
+ * @see Walker::start_lvl()
+ *
+ * @param string $output Used to append additional content. Passed by reference.
+ * @param int $depth Optional. Depth of category. Used for tab indentation. Default 0.
+ * @param array $args Optional. An array of arguments. Will only append content if style argument
+ * value is 'list'. See wp_list_categories(). Default empty array.