Randomly generated string + random selection array summary

The function to generate a random string is as follows

   private function getRandomString($len,$char=null){
        if (is_null($char)){
            $chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        }
        //随机数播种生成器
        //根据参数生成随机数，mt_rand()使用
        //php4.2之后就自动播种，已淘汰
        mt_srand(10000000*(double)microtime());
        for ($i=0,$str=" ",$lc=strlen($chars)-1;$i<$len;$i++){
            $str.=$chars[mt_rand(0,$lc)];
        }
        return $str;
    }

Can self-combined to generate all kinds of data

$user_name= [
            '夏候望',
            '劲冥石',
            '济川烨',
            '欧阳劲',
            '林风眠',
            '伍忘因',
            '赵紫颖',
            '月明溪',
            '风川鸣',
            '欣月馨'
        ];
       
           $name_key=array_rand($user_name);
           
          echo $user_name[$name_key];

The contents of the array can be randomly generated