Discount for a specific product category in WooCommerce cart based on quantity and multiples

Question

The discount I currently have essentially says

• If 6 products within a specific category are in the cart --- discount the total price of $10

This piece of the code works fine. My issue is, this does not work

• If there are 7 products, the 7th product being from a different category.

My goal is to give the discount no matter how many products are in the cart so long as there are 6 products within "Category A".

The following code works so long as there is 6 products in the "discounted category" or there is 1 product with a quantity of 6 etc. It falls apart when I add a product from another category. Feel free to rip it apart.

add_action( 'woocommerce_before_calculate_totals', 'this_item_free' );

function this_item_free() {

    if ( did_action( 'woocommerce_before_calculate_totals' ) >= 2 )
        return;

    $valid_product_category_id = array('soup-mix');
    $has_category = false;

    $count = WC()->cart->get_cart_contents_count();

    foreach ( WC()->cart->get_cart() as $product ) {
        $quantity = $product['quantity'];
        $price = $product['data']->get_price();
    }

    if ( has_term( $valid_product_category_id, 'product_cat', $product['product_id'],
            $product['quantity'] ) ) {
        $has_category = true;
        $cart_total = floatval( preg_replace( '#[^\d.]#', '', WC()->cart->get_cart_total() ) );

        if($count == 6 && $has_category = true){
            add_action( 'woocommerce_cart_calculate_fees', 'discount_based_on_total', 25, 1 );
            function discount_based_on_total( $cart ) {

                $total = $cart->cart_contents_total;
                $discount = 9.95;

                $cart->add_fee( __('discount', 'woocommerce'), -$discount );
                wc_add_notice( apply_filters( 'discount_applied', 'You just got a free soup!') );

            }
        }
    }
}

Answer 1

Your code contains some unnecessary steps and what you want to achieve can be obtained with just the woocommerce_cart_calculate_fees action hook

My answer contains:

Give a discount no matter how many products are in the cart so long as there are 6 products or there is 1 product with a quantity of 6, etc.. within "Category A".

function action_woocommerce_cart_calculate_fees( $cart ) {
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    /* SETTINGS */

    // Specific categories
    $specific_categories = array( 'Categorie-A' );

    // Discount
    $discount = 10;
    
    // Min quantity
    $minimun_quantity = 6;

    /* END SETTINGS */
    
    // Counter
    $current_quantity = 0;

    // Loop though each cart item
    foreach ( $cart->get_cart() as $cart_item ) {
        // Get product id
        $product_id = $cart_item['product_id'];

        // Has certain category     
        if ( has_term( $specific_categories, 'product_cat', $product_id ) ) {
            // Quantity
            $product_quantity = $cart_item['quantity'];

            // Add to total
            $current_quantity += $product_quantity;
        }
    }

    // Greater than or equal to
    if ( $current_quantity >= $minimun_quantity ) {          
        // Add fee
        $cart->add_fee( __( 'Discount_applied', 'woocommerce' ), -$discount, false );      
    }
}
add_action( 'woocommerce_cart_calculate_fees', 'action_woocommerce_cart_calculate_fees', 10, 1 );

---

To apply the discount per 6 products (6 = $10, 12 = $20, 18 = $30, etc..)

Replace

// Greater than or equal to
if ( $current_quantity >= $minimun_quantity ) {          
    // Add fee
    $cart->add_fee( __( 'Discount_applied', 'woocommerce' ), -$discount, false );      
}

With

// Greater than or equal to
if ( $current_quantity >= $minimun_quantity ) {
    // Modulo
    $mod = $current_quantity % $minimun_quantity;
    
    // Times it fit
    $times = ( $current_quantity - $mod ) / $minimun_quantity;

    // Discount * times
    $discount = $discount * $times;
    
    // Add fee
    $cart->add_fee( __( 'Discount_applied', 'woocommerce' ), -$discount, false );      
}