php概率

<?php
/**
 * 全概率计算
 *
 * @param array $ps array('a'=>0.5,'b'=>0.2,'c'=>0.4)
 * @return string 返回上面数组的key
 */
function random($ps)
{
    static $arr = array();
    $key        = md5(serialize($ps));
    if (!isset($arr[$key])) {
        $max = array_sum(array_keys($ps));
        foreach ($ps as $k => $v) {
            $temp = $v['odds'] / $max * 10000;
            for ($i = 0; $i < $temp; $i++) {
                $arr[$key][] = $k;
            }
        }
    }
    return $arr[$key][mt_rand(0, count($arr[$key]) - 1)];
}
$p = [
    5   => ['odds' => (1 / 5000), 'name' => '定制座驾'],
    6   => ['odds' => (1 / 5000), 'name' => '法拉利'],
    7   => ['odds' => (1 / 3000), 'name' => '独角兽'],
    8   => ['odds' => (1 / 5000), 'name' => '月卡'],
    9   => ['odds' => (0 / 5000), 'name' => '季卡'],
    10  => ['odds' => (1 / 2000), 'name' => '年卡'],
    100 => ['odds' => (29984 / 30000), 'name' => '没有中奖'],
];
$data = [];
for ($i = 0; $i < 1000; $i++) {
    $key = random($p);
    echo $key;
    echo "==";
    if (isset($data[$key])) {
        $data[$key]++;
    } else {
        $data[$key] = 1;
    }
}
var_dump($data);
php概率

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