WC_Tax::sort_rates_callback PHP Method

    private static function sort_rates_callback($rate1, $rate2)
    {
        if ($rate1->tax_rate_priority !== $rate2->tax_rate_priority) {
            return $rate1->tax_rate_priority < $rate2->tax_rate_priority ? -1 : 1;
            // ASC
        } elseif ($rate1->tax_rate_country !== $rate2->tax_rate_country) {
            if ('' === $rate1->tax_rate_country) {
                return 1;
            }
            if ('' === $rate2->tax_rate_country) {
                return -1;
            }
            return strcmp($rate1->tax_rate_country, $rate2->tax_rate_country) > 0 ? 1 : -1;
        } elseif ($rate1->tax_rate_state !== $rate2->tax_rate_state) {
            if ('' === $rate1->tax_rate_state) {
                return 1;
            }
            if ('' === $rate2->tax_rate_state) {
                return -1;
            }
            return strcmp($rate1->tax_rate_state, $rate2->tax_rate_state) > 0 ? 1 : -1;
        } else {
            return $rate1->tax_rate_id < $rate2->tax_rate_id ? -1 : 1;
            // Identical - use ID
        }
    }