tp5生成6位不重复验证码

/**
     * 获取激活码
     */
    public function getnum()
    {
        $time = Db::name('fangchan_jihuoma')->group('id desc')->limit(1)->find();//从上一次生成的时间开始计算
        $num='';
        if(empty($time)){
            $num = microtime(true);
        }else{
            $num = $time['info_time'];
        }
        for ($i = $num; $i < ($num + 5); $i++) {
//            dump(substr(md5($i), 0, 6));exit;
            Db::name("fangchan_jihuoma")->insert([
                'num' => substr(md5($i), 0, 6),
                'status' => '',
                'created_time' => time(),
                'info_time' => $i
            ]);
        }
        $sql = "select count(*) as sum,num from osc_fangchan_jihuoma group by num HAVING sum>1";//查出有多少个重复的验证码和重复验证码内容
        $data = Db::query($sql);
        if(!empty($data)) {
            foreach($data as $k=> $v) {
                for($j=0;$j<$v['sum'];$j++){
                    Db::name("fangchan_jihuoma")->where('num',1)->where('status',0)->delete();删除重复的验证码
                }
            }
        }
        $this->success('激活码已生成！');
    }