guidv4 with random_bytes()

guidv4.php

<?php
function guidv4()
{
    if (function_exists('random_bytes') === true) {
        $bytes = random_bytes(16);
    } elseif (function_exists('openssl_random_pseudo_bytes') === true) {
        $bytes = openssl_random_pseudo_bytes(16);
    } elseif (function_exists('mcrypt_create_iv') === true) {
        $bytes = mcrypt_create_iv(16, MCRYPT_DEV_URANDOM);
    } elseif (function_exists('com_create_guid') === true) {
        return trim(com_create_guid(), '{}');
    } else {
        return sprintf(
            '%04x%04x-%04x-%04x-%04x-%04x%04x%04x', 
            mt_rand(0, 65535), 
            mt_rand(0, 65535), 
            mt_rand(0, 65535), 
            mt_rand(16384, 20479), 
            mt_rand(32768, 49151), 
            mt_rand(0, 65535), 
            mt_rand(0, 65535), 
            mt_rand(0, 65535)
        );
    }

    $bytes[6] = chr(ord($bytes[6]) & 0x0f | 0x40); // set version to 0100
    $bytes[8] = chr(ord($bytes[8]) & 0x3f | 0x80); // set bits 6-7 to 10
    return vsprintf('%s%s-%s-%s-%s-%s%s%s', str_split(bin2hex($bytes), 4));
}