//概率计算函数
    public function get_rand($proArr) {
        $result = ‘‘;  
        //概率数组的总概率精度
        $proSum = array_sum($proArr);  
        //概率数组循环
        foreach ($proArr as $key => $proCur) {
            $randNum = mt_rand(1, $proSum);
            if ($randNum <= $proCur) {
                $result = $key;
                break;
            } else {
                $proSum -= $proCur;
            }
        }
        unset ($proArr);   
        return $result;
    }