Tutorial: Assign Existing WooCommerce Categories to a New Parent Category Programmatically

If you already have categories in WooCommerce and want to group them under a newly created parent category programmatically, this guide is for you. We’ll create a parent category and then reassign existing categories to it as children.

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Overview

1. Create a new parent category.
2. Reassign existing categories as children to this new parent category.
3. Verify the updated category hierarchy.

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Step 1: Create a New Parent Category

We’ll use wp_insert_term() to create a new parent category.

Code Example: Creating the Parent Category

function create_new_parent_category() {
    // Check if the parent category already exists
    if (!term_exists('Footwear', 'product_cat')) {
        wp_insert_term(
            'Footwear', // Category Name
            'product_cat', // Taxonomy
            array(
                'description' => 'A collection of all types of footwear.',
                'slug' => 'footwear', // URL-friendly slug
                'parent' => 0, // 0 indicates this is a top-level category
            )
        );
    }
}
add_action('init', 'create_new_parent_category');

What’s Happening Here

• term_exists() checks if the category already exists to avoid duplicates.
• parent => 0 ensures this is a top-level category.

After running this, you’ll have a new parent category called Footwear.

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Step 2: Reassign Existing Categories to the New Parent

We’ll now fetch the IDs of existing categories and set their parent to the new category.

Code Example: Assign Existing Categories to the New Parent

function assign_categories_to_parent() {
    // Get the parent category ID
    $parent_category = get_term_by('slug', 'footwear', 'product_cat');

    if ($parent_category) {
        // List of existing category slugs to assign
        $child_category_slugs = array('shoes', 'sandals', 'boots');

        foreach ($child_category_slugs as $slug) {
            $category = get_term_by('slug', $slug, 'product_cat');
            
            if ($category) {
                wp_update_term(
                    $category->term_id, // ID of the category to update
                    'product_cat', // Taxonomy
                    array(
                        'parent' => $parent_category->term_id, // Set the new parent
                    )
                );
            }
        }
    }
}
add_action('init', 'assign_categories_to_parent');

What’s Happening Here

1. get_term_by() retrieves the new parent category’s ID.
2. wp_update_term() updates each child category’s parent to the new parent category’s ID.
3. Replace the child_category_slugs array with the slugs of your existing categories.

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Step 3: Verify the Hierarchy

After running the code:

1. Go to Products > Categories in the WordPress admin.
2. Check that the selected categories (e.g., Shoes, Sandals, Boots) are now subcategories of the new parent category (e.g., Footwear).

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Optional: Display the Updated Category Hierarchy

To confirm everything is working on the front end, you can display the hierarchy dynamically.

Code Example: Display Updated Hierarchy

function display_updated_category_hierarchy() {
    $args = array(
        'taxonomy' => 'product_cat',
        'orderby' => 'name',
        'order' => 'ASC',
        'hide_empty' => false,
    );

    $categories = get_terms($args);

    if (!empty($categories)) {
        echo '<ul class="product-categories">';
        foreach ($categories as $category) {
            if ($category->parent == 0) {
                // Display top-level categories
                echo '<li>' . esc_html($category->name);

                // Fetch child categories
                $child_args = array(
                    'taxonomy' => 'product_cat',
                    'parent' => $category->term_id,
                    'hide_empty' => false,
                );
                $child_categories = get_terms($child_args);

                if (!empty($child_categories)) {
                    echo '<ul>';
                    foreach ($child_categories as $child) {
                        echo '<li>' . esc_html($child->name) . '</li>';
                    }
                    echo '</ul>';
                }

                echo '</li>';
            }
        }
        echo '</ul>';
    }
}
add_action('woocommerce_before_shop_loop', 'display_updated_category_hierarchy');

What’s Happening Here

• Top-level categories are fetched and displayed first.
• Child categories are retrieved and nested within their parent category.

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Testing the Code

1. Activate the Code: Save changes to your theme’s functions.php file or custom plugin.
2. Visit the Categories Page:
   • Verify the hierarchy under Products > Categories.
3. View the Store:
   • Check the front-end display (if you’ve added the display code).

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Conclusion

You’ve now successfully created a new parent category and assigned existing categories as children programmatically. This approach is perfect for automating category organization, especially for large catalogs.

Need help fine-tuning the process or troubleshooting? Let me know! 🚀