商品活动抽奖概率算法

商品抽奖概率算法。可用于随机抽取一定概率的商品。

public function rand_rate($data)
    {
        $roll = rand(1, array_sum($data));
        $tmp = 0;
        $rollnum = 0;
        foreach ($data as $k => $v) {
            $min = $tmp;
            $tmp += $v;
            $max = $tmp;
            if ($roll > $min && $roll <= $max) {
                $rollnum = $k;
                break;
            }
        }
        return $rollnum;
    }