Ajax Action function

function abcbiz_ajax_add_to_cart_handler() {

    if (!isset($_POST['abcbiz_cart_nonce']) || !wp_verify_nonce($_POST['abcbiz_cart_nonce'], 'abcbiz_add_to_cart_nonce')) {
        wp_send_json_error(['message' => 'Nonce verification failed.']);
        return;
    }

    if (!isset($_POST['product_id'])) {
        wp_send_json_error(['message' => 'Product ID is missing.']);
        return;
    }

    $product_id = (int) $_POST['product_id'];
    $quantity = isset($_POST['quantity']) ? (int) $_POST['quantity'] : 1; // Use sent quantity or default to 1

    if (!wc_get_product($product_id)) {
        wp_send_json_error(['message' => 'Invalid product.']);
        return;
    }

    $cart_item_key = WC()->cart->add_to_cart($product_id, $quantity);

    if ($cart_item_key) {
        wp_send_json_success(['message' => 'Product successfully added to cart.']);
    } else {
        wp_send_json_error(['message' => 'Failed to add the product to the cart.']);
    }
}
add_action('wp_ajax_abcbiz_ajax_add_to_cart_handler', 'abcbiz_ajax_add_to_cart_handler');
add_action('wp_ajax_nopriv_abcbiz_ajax_add_to_cart_handler', 'abcbiz_ajax_add_to_cart_handler');