How to Implement a WooCommerce BOGO: Buy a Fixed Quantity from Both Category X & Y, Get One Free from Category Z?

This customization is useful in implementing promotions targeting the product quantity as well as certain categories. For instance, an online electronic store might have a variety of categories such as SmartPhone(X), Laptop(Y), Electronic(Z), etc. The promotion works when the following condition is met. i.e. when products from both categories X and Y are bought in a fixed quantity number, a free product from the category Z is offered.

add_action('woocommerce_add_to_cart', 'ts_add_product_cat', 10, 2);

function ts_add_product_cat($cart_item_key, $product_id) {
    $category_ids_to_buy = array(50, 65); // Categories X and Y
    $free_category_id = 63; // Category Z
    $required_quantity = 4; // Total combined quantity required to trigger free product

    // Initialize counters for each category
    $category_counts = array_fill_keys($category_ids_to_buy, 0);

    // Update counters based on items in the cart
    foreach (WC()->cart->get_cart() as $cart_item) {
        $cart_product_cats_ids = wc_get_product_term_ids($cart_item['product_id'], 'product_cat');
        foreach ($category_ids_to_buy as $cat_id) {
            if (in_array($cat_id, $cart_product_cats_ids)) {
                $category_counts[$cat_id] += $cart_item['quantity'];
            }
        }
    }

    // Check if the combined count of products from categories X and Y meets or exceeds the required quantity
    $total_quantity = array_sum($category_counts);
    if ($total_quantity >= $required_quantity) {
        // Check if there's a free product in the cart already, if not, add one
        $free_product_in_cart = false;
        foreach (WC()->cart->get_cart() as $cart_item) {
            $cart_product_cats_ids = wc_get_product_term_ids($cart_item['product_id'], 'product_cat');
            if (in_array($free_category_id, $cart_product_cats_ids)) {
                $free_product_in_cart = true;
                break;
            }
        }

        // If there's no free product in the cart, add one
        if (!$free_product_in_cart) {
            // Get a free product from the specified category
            $free_product_id = ts_get_free_product_from_category($free_category_id);

            // If the free product is available, add it to the cart
            if ($free_product_id) {
                WC()->cart->add_to_cart($free_product_id);
            }
        }
    }
} 

function ts_get_free_product_from_category($category_id) {
    // Implement this function to dynamically get a free product ID from the specified category
    $args = array(
        'post_type' => 'product',
        'posts_per_page' => 1,
        'tax_query' => array(
            array(
                'taxonomy' => 'product_cat',
                'field' => 'id',
                'terms' => $category_id,
            ),
        ),
    );

    $products_query = new WP_Query($args);

    if ($products_query->have_posts()) {
        $products_query->the_post();
        $free_product_id = get_the_ID();
        wp_reset_postdata();
        return $free_product_id;
    }

    return null; // Return null if no free product is found
}

    

Output

When customers purchase items meeting the total combined quantity of 4 as specified in the code($required_quantity = 4;) from both categories X and Y (Smartphone+Laptop), the free product from Category Z (Electronic Accessories) will be automatically added to the cart.

If the total quantity of products from the specified categories of X and Y is not reached, then the free product will not be added.

Likewise, you can also offer discounts on category Y when purchasing category X within a specified quantity range in WooCommerce.