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

<?php$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 ]];

•  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

<?php$thanks_prize = ['id' => 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

<?php$pay_total = 7000;foreach ($prize as $key => $value) {if($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

<?php$now_chance = array_sum(array_column($prize, 'chance'));$remain_chance = 10000 - $now_chance;$prize[] = ['id' => 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

<?php$rand = mt_rand(1, 10000);$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;}}}

• 开始抽奖，并返回抽中的结果

六、过滤回调

<?php//此处应该查询数据库，查看该奖品已经抽中的数量$yet_num = 50;if($result['pid'] != 0 && $yet_num > $result['total']) {$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

<?php//删除敏感字段unset($result['total'],$result['chance'],$result['daynum'],$result['pay']);//返回最终抽奖结果echo json_encode(['prize' => $award,'rand' => $rand,'result' => $result]);

八、抽奖封装成类

<?php/*** Created by PhpStorm.* User: autofelix* Date: 2020/10/30* Time: 13:14* Desc: 抽奖算法*/class Lottery{/*** 概率基数* @var int*/private $total_chance = 10000;/*** 谢谢参与奖励* @var array*/private $thanks_prize = ['id' => 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());