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Home > List of blog posts > php实现自定义中奖项数和概率的抽奖函数示例
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php实现自定义中奖项数和概率的抽奖函数示例
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本文实例讲述了php实现自定义中奖项数和概率的抽奖函数。分享给大家供大家参考，具体如下：

<?php

/*

* 一个抽奖类，精确到万分之一

* 三个步骤：1.接受一个中奖概率数组;2.接受一个抽奖种子;3.返回中奖等级

*/

class Lottery {

/*

* 中奖概率数组，自动判断奖项数目

* 数组键值和为100，自动计算出不中奖的概率，若初始是超过100抛出一个错误

*/

protected $_rate = array();

/*

* 设置中奖概率，

* @param Array,中奖概率，以数组形式传入

*/

public function setRate($rate = array(12.1, 34)) {

$this->_rate = $rate;

if (array_sum($this->_rate) > 100)//检测概率设置是否有问题

throw new Exception('Winning rate upto 100%');

if (array_sum($this->_rate) < 100)

//定义未中奖情况的概率，用户给的概率只和为100时，则忽略0

$this->_rate[] = 100 - array_sum($this->_rate);

}

/*

* 随机生成一个1-10000的整数种子，提交给中奖判断函数

* @return int,按传入的概率排序，返回中奖的项数

*/

public function runOnce() {

return $this->judge(mt_rand(0, 10000));

}

/*

* 按所设置的概率，判断一个传入的随机值是否中奖

* @param int,$seed 10000以内的随机数

* @return int,$i 按传入的概率排序，返回中奖的项数

*/

protected function judge($seed) {

foreach ($this->_rate as $key => $value) {

$tmpArr[$key + 1] = $value * 100;

}

//将概率乘十后累计，以便随机选择，组合成

$tmpArr[0] = 0;

foreach ($tmpArr as $key => $value) {

if ($key > 0) {

$tmpArr[$key] += $tmpArr[$key - 1];

}

}

for ($i = 1; $i < count($tmpArr); $i++) {

if ($tmpArr[$i - 1] < $seed && $seed <= $tmpArr[$i]) {

return $i; //返回中奖的项数（按概率的设置顺序）

}

}

}

}

$rate = array(33, 20, 2, 0.95, 12, 4.55);

$a = new Lottery;

$a->setRate($rate);

for ($i = 0; $i <= 10000; $i++) {

$b = $a->runOnce();

@$rewards[$b]++;

}

unset($rewards['']);

echo array_sum($rewards);

?>

<html>

<head>

<meta http-equiv="Content-Type" content="text/html; charset=utf8" />

</head>

<body>

<table>

<thead>运行10000次，对比设置概率和中奖次数</thead>

<tr><th>设置概率</th><th>中奖次数</th></tr>

<tr><td><?php echo $rate[0]; ?>%</td><td><?php echo $rewards[1] ?></td></tr>

<tr><td><?php echo $rate[1]; ?>%</td><td><?php echo $rewards[2] ?></td></tr>

<tr><td><?php echo $rate[2]; ?>%</td><td><?php echo $rewards[3] ?></td></tr>

<tr><td><?php echo $rate[3]; ?>%</td><td><?php echo $rewards[4] ?></td></tr>

<tr><td><?php echo $rate[4]; ?>%</td><td><?php echo $rewards[5] ?></td></tr>

<tr><td><?php echo $rate[5]; ?>%</td><td><?php echo $rewards[6] ?></td></tr>

<tr><td><?php echo 'miss'; ?></td><td><?php echo $rewards[7] ?></td></tr>

</table>

</body>

</html>


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