WooCommerce Product Settings: Enabling Custom Discount Options with Checkbox and Input Field First set quantity only – No Plugin

// Add checkbox and input field to general tab

add_action('woocommerce_product_options_general_product_data', 'add_custom_fields_to_general_tab');

function add_custom_fields_to_general_tab() {

    global $post;

    // Retrieve the current values of the checkbox and input field

    $checked = get_post_meta($post->ID, '_allow_discount', true);

    $required_quantity = get_post_meta($post->ID, '_required_quantity', true);

    // Output the checkbox HTML

    woocommerce_wp_checkbox(array(

        'id' => '_allow_discount',

        'label' => __('Allow Discount'),

        'description' => __('Check this box to allow the "E.g buy 3x, get 1 free first set only" discount on this product.'),

        'value' => $checked,

    ));

    echo '<div class="options_group">';

    // Output the input field HTML

    woocommerce_wp_text_input(array(

        'id' => '_required_quantity',

        'label' => __('Required Quantity for Discount'),

        'description' => __('Enter the number of products required for the discount to apply.'),

        'type' => 'number',

        'custom_attributes' => array(

            'step' => '1',

            'min' => '1',

            'value' => $required_quantity,

        ),

    ));

    echo '</div>';

}

// Save checkbox and input field values when product is saved

add_action('woocommerce_process_product_meta', 'save_custom_fields_values');

function save_custom_fields_values($post_id) {

    $checkbox_value = isset($_POST['_allow_discount']) ? 'yes' : 'no';

    $required_quantity_value = isset($_POST['_required_quantity']) ? intval($_POST['_required_quantity']) : 0;

    update_post_meta($post_id, '_allow_discount', $checkbox_value);

    update_post_meta($post_id, '_required_quantity', $required_quantity_value);

}

// Apply custom discount label to specific products

add_action('woocommerce_cart_calculate_fees', 'apply_custom_discount');

function apply_custom_discount() {

    if (is_admin() && !defined('DOING_AJAX'))

        return;

    // Get the cart instance

    $cart = WC()->cart;

    // Initialize variables

    $discount_amount = 0;

    $applied_discount = false;

    // Loop through cart items

    foreach ($cart->get_cart() as $cart_item) {

        $product_id = $cart_item['product_id'];

        $allow_discount = get_post_meta($product_id, '_allow_discount', true);

        $required_quantity = get_post_meta($product_id, '_required_quantity', true);

        $quantity_in_cart = $cart_item['quantity'];

        if (!$applied_discount && $allow_discount === 'yes' && $quantity_in_cart >= ($required_quantity + 1)) {

            // Calculate the number of free products

            $free_product_count = 1;

            // Calculate discount amount for the first X products

            $discount_amount = $cart_item['data']->get_price() * $free_product_count;

            // Apply discount with custom label

            $discount_label = __('Buy x Get +1pc Discount', 'your-text-domain'); // Replace 'your-text-domain' with your theme or plugin text domain

            $cart->add_fee($discount_label, -$discount_amount);

            $applied_discount = true;

            break;

        }

    }

}

// Display notice on the front end of the product

add_action('woocommerce_after_add_to_cart_button', 'display_product_discount_notice');

function display_product_discount_notice() {

    global $product;

    // Retrieve the product ID

    $product_id = $product->get_id();

    // Retrieve the values of the checkbox and input field

    $allow_discount = get_post_meta($product_id, '_allow_discount', true);

    $required_quantity = get_post_meta($product_id, '_required_quantity', true);

    if ($allow_discount === 'yes' && $required_quantity > 0) {

        $discount_notice = sprintf(

            __('Buy %s+1 Get 1pc Free Discount', 'your-text-domain'), // Replace 'your-text-domain' with your theme or plugin text domain

            $required_quantity,

            $required_quantity

        );

        // Output the discount notice with updated styles

        echo '<div style="width: 100%; margin-top: 10px; box-sizing: border-box; display: flex; justify-content: center;">

                <div style="background-color: #4CAF50; color: white; padding: 10px; font-size: 16px; border-radius: 5px; text-align: center;">' . esc_html($discount_notice) . '</div>

              </div>';

    }

}