What are the best practices for organizing and structuring child categories within a PHP metabox?

When organizing and structuring child categories within a PHP metabox, it is important to ensure that the hierarchy is clear and easy to navigate for users. One way to achieve this is by using a recursive function to display parent and child categories in a nested format within the metabox.

function display_categories_hierarchy($parent_id = 0, $level = 0) {
    $categories = get_categories(array('parent' => $parent_id));

    foreach ($categories as $category) {
        echo str_repeat('-', $level) . $category->name . '<br>';
        display_categories_hierarchy($category->term_id, $level + 1);
    }
}

add_action('add_meta_boxes', 'add_custom_metabox');

function add_custom_metabox() {
    add_meta_box('category_hierarchy_metabox', 'Category Hierarchy', 'display_categories_metabox', 'post');
}

function display_categories_metabox() {
    echo '<div>';
    display_categories_hierarchy();
    echo '</div>';
}