概率抽奖算法

适用于抽奖、随机广告等需要按概率从一组数据中取出一个的场景。

代码实例：

function getProbabilityPrizeId($prize_info)
{
    $prize_arr = [];
    foreach ($prize_info as $key => $val) {
        $prize_arr[$val['id']] = bcmul($val['probability'], '1000', 0);
    }
    //概率数组的总概率精度
    $proSum = array_sum($prize_arr);
    //概率数组循环
    $randNum = mt_rand(1, $proSum);
    foreach ($prize_arr as $key => $proCur) {
        $randNum -= $proCur;
        if ($randNum <= 0) {
            $prizeId = $key;
            break;
        }
    }
    return $prizeId;
}

$prize_arr = [
    ['id' => 1, 'prize' => '平板电脑', 'probability' => 1],
    ['id' => 2, 'prize' => '数码相机', 'probability' => 5],
    ['id' => 3, 'prize' => '音箱设备', 'probability' => 10],
    ['id' => 4, 'prize' => '4G优盘', 'probability' => 12],
    ['id' => 5, 'prize' => '10Q币', 'probability' => 22],
    ['id' => 6, 'prize' => '下次没准就能中哦', 'probability' => 50],
];

var_dump(getProbabilityPrizeId($prize_arr));