public function symbol()
    {
        switch ($this->suit) {
            case static::CLUB:
                $symbol = self::CLUB_SYMBOL;
                break;
            case static::DIAMOND:
                $symbol = self::DIAMOND_SYMBOL;
                break;
            case static::HEART:
                $symbol = self::HEART_SYMBOL;
                break;
            default:
            case static::SPADE:
                $symbol = self::SPADE_SYMBOL;
                break;
        }

        return $symbol;
    }