生成数据库的随机ID

Question

I have a requirement on a project where

• I need to generate unique ID's.
• ID's must be upper case.
• I cannot check database to see if ID has been used previously.

We expect to have many millions of records added to database every month.

I have tried solutions here: PHP: How to generate a random, unique, alphanumeric string? and while they seem to work at first, my testing has shown there would be duplicates over time.

Now I am looking at using uniqid with a prefix. The problem I found using uniqid without a prefix is that duplicates will be generated when simultaneous requests come into server at the same exact time. I am hoping using a prefix would solve this.
I am thinking of using this function:

private function generate_id()
{
    $alpha_numeric = 'ABCDEFGHIJKLMNPQRSTUVWXYZ0123456789';
    $max = strlen($alpha_numeric);
    $prefix = '';

    for ($i = 0; $i < 5; $i++)
    {
        $prefix .= $alpha_numeric[random_int(0, $max - 1)];
    }
    return strtoupper(uniqid($prefix));
}

The prefix would be a 5 character alphanumeric string. Would this be enough to satisfy my requirements?

*****Edit*****

Using a UUID as suggested would be the best way to limit the chance of collision but it has been decided to go with the approach above but increase the prefix to 7 characters. The chance of a collision if two ID's where generated at the same millisecond would be around 1 in 8.3 million. That has been deemed acceptable by the higher ups.

Answer 1

If you use Composer or external libraries see https://github.com/ramsey/uuid

or this function may meet your needs. For your needs strtoupper the result:

/**
 * generate
 *
 * Returns a version 4 UUID
 *
 * @access public
 * @return string
 */
public static function generate()
{
    $data = openssl_random_pseudo_bytes(16);

    $data[6] = chr(ord($data[6]) & 0x0f | 0x40); // set version to 0100
    $data[8] = chr(ord($data[8]) & 0x3f | 0x80); // set bits 6-7 to 10

    return vsprintf('%s%s-%s-%s-%s-%s%s%s', str_split(bin2hex($data), 4));
}

See https://en.wikipedia.org/wiki/Universally_unique_identifier#Version_4_(random)