NEVER USE this UUIDv4 generator

genuuid4.php

#!/usr/bin/env php
<?php
/**
 * composer init && composer require cakephp/utility:^3.8
 *
 * Try < PHP 5.6: ./genuuid4.php 65536 | sort | uniq -d
 */
require 'vendor/autoload.php';

use Cake\Utility\Text;

function make_seed()
{
    list($usec, $sec) = explode(' ', microtime());

    return $sec + $usec * 1000000;
}

$repeats = isset($argv[1]) ? (int)$argv[1] : 1;
for ($i = 0; $i < $repeats; $i++) {
    mt_srand(make_seed()); // !! HAHAHAHAHHHAHA !!
    echo Text::uuid() . "\n";
}

なるほど。 > メルセンヌツイスタはそんなに衝突しない - Qiita https://qiita.com/blackenedgold/items/52da300456b1e6e1365a