walk_page_tree example

        global $wp_query;
        if ( is_page() || is_attachment() || $wp_query->is_posts_page ) {
            $current_page = get_queried_object_id();
        } elseif ( is_singular() ) {
            $queried_object = get_queried_object();
            if ( is_post_type_hierarchical( $queried_object->post_type ) ) {
                $current_page = $queried_object->ID;
            }
        }

        $output .= walk_page_tree( $pages, $parsed_args['depth'], $current_page, $parsed_args );

        if ( $parsed_args['title_li'] ) {
            $output .= '</ul></li>';
        }
    }

    /** * Filters the HTML output of the pages to list. * * @since 1.5.1 * @since 4.4.0 `$pages` added as arguments. * * @see wp_list_pages() * * @param string $output HTML output of the pages list. * @param array $parsed_args An array of page-listing arguments. See wp_list_pages() * for information on accepted arguments. * @param WP_Post[] $pages Array of the page objects. */