WC_Cart::generate_cart_id PHP Method

    public function generate_cart_id($product_id, $variation_id = 0, $variation = array(), $cart_item_data = array())
    {
        $id_parts = array($product_id);
        if ($variation_id && 0 != $variation_id) {
            $id_parts[] = $variation_id;
        }
        if (is_array($variation) && !empty($variation)) {
            $variation_key = '';
            foreach ($variation as $key => $value) {
                $variation_key .= trim($key) . trim($value);
            }
            $id_parts[] = $variation_key;
        }
        if (is_array($cart_item_data) && !empty($cart_item_data)) {
            $cart_item_data_key = '';
            foreach ($cart_item_data as $key => $value) {
                if (is_array($value) || is_object($value)) {
                    $value = http_build_query($value);
                }
                $cart_item_data_key .= trim($key) . trim($value);
            }
            $id_parts[] = $cart_item_data_key;
        }
        return apply_filters('woocommerce_cart_id', md5(implode('_', $id_parts)), $product_id, $variation_id, $variation, $cart_item_data);
    }