Why is the result of Alibaba Cloud server’s random number generation fixed?

The random number generation result is always the same on Alibaba Cloud
No problem locally

<code>public function randStr($len = 6, $format = 'ALL') {
    switch ($format) {
        case 'ALL':
            $chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-@#~';
            break;
        case 'CHAR':
            $chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-@#~';
            break;
        case 'NUMBER':
            $chars = '0123456789';
            break;
        default :
            $chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-@#~';
            break;
    }
    mt_srand((double) microtime() * 1000000 * getmypid());
    $password = "";
    while (strlen($password) < $len) {
        $password.=substr($chars, (mt_rand() % strlen($chars)), 1);
    }
    return $password;
}</code>

Reply content:

The random number generation result is always the same on Alibaba Cloud
No problem locally

<code>public function randStr($len = 6, $format = 'ALL') {
    switch ($format) {
        case 'ALL':
            $chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-@#~';
            break;
        case 'CHAR':
            $chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-@#~';
            break;
        case 'NUMBER':
            $chars = '0123456789';
            break;
        default :
            $chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-@#~';
            break;
    }
    mt_srand((double) microtime() * 1000000 * getmypid());
    $password = "";
    while (strlen($password) < $len) {
        $password.=substr($chars, (mt_rand() % strlen($chars)), 1);
    }
    return $password;
}</code>

It is recommended not to use mt_srand((double) microtime() * 1000000 * getmypid()); to spread random seeds. Now this function can be completed automatically. In addition, the value you sow is fixed.

There is no problem with the code. I have tested it both on the Alibaba Cloud server and locally. The chance of the same seeds is already very low.

php7 uses random-int