还在抱怨王者荣耀水晶难抽？PHP一文带你搞懂游戏中的抽奖算法

前言： 没有特别幸运，那么请先特别努力，别因为懒惰而失败，还矫情地将原因归于自己倒霉。你必须特别努力，才能显得毫不费力。

希望：所以说，树倒了，没有一片雪花是无辜的，抽奖都是假的，只有人家想让你中和不想让你中，如果大家觉得文章有帮助，请给博主一波关注和评论。

目录

一、初始化奖品

二、谢谢参与

三、过滤抽奖、如充值条件

四、重组概率

五、进行抽奖

六、过滤回调

七、最终抽奖结果

八、抽奖封装成类

---

一、初始化奖品

• id 奖品的id
• pid 奖品的自定义id
• type 奖品类型，1、虚拟奖品 2、实物奖品 3、礼包码 待扩充
• name 奖品名称
• total 奖品总数
• chance 获奖概率/抽奖基数10000
• daynum 每日数量限制
• pay 充值限制

 1, 'pid' => 11, 'type' => 1, 'name' => '典藏英雄', 'total' => 20, 'chance' => 1000, 'daynum' => 10, 'pay' => 2000 ],
    ['id' => 2, 'pid' => 12, 'type' => 1, 'name' => '史诗皮肤', 'total' => 40, 'chance' => 1000, 'daynum' => 10, 'pay' => 4000 ],
    ['id' => 3, 'pid' => 13, 'type' => 1, 'name' => '钻石奖励', 'total' => 80, 'chance' => 1000, 'daynum' => 10, 'pay' => 4000 ],
    ['id' => 4, 'pid' => 14, 'type' => 1, 'name' => '荣耀水晶', 'total' => 20, 'chance' => 1000, 'daynum' => 10, 'pay' => 8000 ]
];

•  奖品详情应该从数据库中读出来
• 奖品详情应该加入缓存，避免数据库的压力

二、谢谢参与

 0,
    'pid' => 0,
    'type' => 1,
    'name' => '谢谢参与'
];

•  为填充剩余概率的奖品

三、过滤抽奖、如充值条件

 $value) {
    if($value['pay'] > $pay_total) unset($prize[$key]);
}

•  初步过滤一些必要因素，比如充值，角色创建时间等

四、重组概率

 0, 'pid' => 0, 'type' => 1, 'name' => '谢谢参与', 'total' => 0, 'chance' => $remain_chance, 'daynum' => 0, 'pay' => 0];

$award = [];
$num = 0;
foreach ($prize as $_v) {
    $num += $_v['chance'];
    $award[] = ['id' => $_v['id'], 'pid' => $_v['pid'], 'type' => $_v['type'], 'name' => $_v['name'], 'total' => $_v['total'], 'chance' => $num, 'daynum' => $_v['daynum'], 'pay' => $_v['pay']];
}

•  初步过滤后，重构新的抽奖信息，加入谢谢参与
• 第二步重组概率

五、进行抽奖

 $_v) {
    if ($_k == 0) {
        if ($rand > 0 && $rand <= $_v['chance']) {
            $result = $_v;
            break;
        }
    } else {
        if ($rand > $award[$_k - 1]['chance'] && $rand <= $_v['chance']) {
            $result = $_v;
            break;
        }
    }
}

• 开始抽奖，并返回抽中的结果

六、过滤回调

 $result['total']) {
    $result = $thanks_prize;
}

//此处应该查询数据库，查看该奖品今日已经抽中的数量
$yet_today_num = 50;
if($result['pid'] != 0 && $yet_today_num > $result['daynum']) {
    $result = $thanks_prize;
}

• 二次过滤，奖品总数的限制以及奖品的每日限制等 

七、最终抽奖结果

 $award,
    'rand' => $rand,
    'result' => $result
]);

八、抽奖封装成类

 0,
        'pid' => 0,
        'type' => 1,
        'name' => '谢谢参与'
    ];

    /**
     * 奖池
     * @var array
     */
    private $prize = [
        ['id' => 1, 'pid' => 11, 'type' => 1, 'name' => '典藏英雄', 'total' => 20, 'chance' => 1000, 'daynum' => 10, 'pay' => 2000 ],
        ['id' => 2, 'pid' => 12, 'type' => 1, 'name' => '史诗皮肤', 'total' => 40, 'chance' => 1000, 'daynum' => 10, 'pay' => 4000 ],
        ['id' => 3, 'pid' => 13, 'type' => 1, 'name' => '钻石奖励', 'total' => 80, 'chance' => 1000, 'daynum' => 10, 'pay' => 4000 ],
        ['id' => 4, 'pid' => 14, 'type' => 1, 'name' => '荣耀水晶', 'total' => 20, 'chance' => 1000, 'daynum' => 10, 'pay' => 8000 ]
    ];

    /**
     * Lottery constructor.
     */
    public function __construct()
    {
    }

    /**
     * @return int
     */
    private function get_user_pay()
    {
        //这里应该调用接口，返回用户正确的充值信息
        return 3000;
    }

    /**
     * 重构奖池、重组概率
     * @return array
     */
    private function init_lottery_pond()
    {
        $award = [];

        //充值限制
        $user_pay = $this->get_user_pay();
        foreach ($this->prize as $key => $value) {
            if($value['pay'] <= $user_pay) unset($this->prize[$key]);
        }

        //加入谢谢惠顾
        $now_chance = array_sum(array_column($this->prize, 'chance'));
        $remain_chance = $this->total_chance - $now_chance;
        $this->prize[] = ['id' => 0, 'pid' => 0, 'type' => 1, 'name' => '谢谢参与', 'total' => 0, 'chance' => $remain_chance, 'daynum' => 0, 'pay' => 0];

        //重组概率
        $num = 0;
        foreach ($this->prize as $_v) {
            $num += $_v['chance'];
            $award[] = ['id' => $_v['id'], 'pid' => $_v['pid'], 'type' => $_v['type'], 'name' => $_v['name'], 'total' => $_v['total'], 'chance' => $num, 'daynum' => $_v['daynum'], 'pay' => $_v['pay']];
        }

        return $award;
    }

    /**
     * 获取抽奖结果
     * @return array
     */
    public function get_prize()
    {
        $award = $this->init_lottery_pond();
        $rand = mt_rand(1, $this->total_chance);
        $result = [];
        foreach ($award as $_k => $_v) {
            if ($_k == 0) {
                if ($rand > 0 && $rand <= $_v['chance']) {
                    $result = $_v;
                    break;
                }
            } else {
                if ($rand > $award[$_k - 1]['chance'] && $rand <= $_v['chance']) {
                    $result = $_v;
                    break;
                }
            }
        }

        $result = $this->filter($result);
        return $result;
    }

    /**
     * 抽奖过滤回调函数
     * @param $result
     * @return array
     */
    public function filter($result)
    {
        //奖品总数限制，此处应该查数据库
        $yet_num = 50;
        if($result['pid'] != 0 && $yet_num > $result['total']) {
            $result = $this->thanks_prize;
        }

        //奖品每日数量限制，此处应该查数据库
        $yet_today_num = 50;
        if($result['pid'] != 0 && $yet_today_num > $result['daynum']) {
            $result = $this->thanks_prize;
        }

        //不暴露敏感信息
        unset($result['total'], $result['chance'], $result['daynum'], $result['pay'] );
        return $result;
    }

    private function __clone()
    {
    }
}

echo json_encode((new Lottery())->get_prize());