php[world] 2019 — 25 years of PHP

com_create_guid

(PHP 5, PHP 7)

com_create_guidGenerate a globally unique identifier (GUID)

Description

com_create_guid ( void ) : string

Generates a Globally Unique Identifier (GUID).

A GUID is generated in the same way as DCE UUID's, except that the Microsoft convention is to enclose a GUID in curly braces.

Return Values

Returns the GUID as a string.

See Also

  • uuid_create() in the PECL uuid extension

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User Contributed Notes 4 notes

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29
pavel.volyntsev(at)gmail
3 years ago
Use more cryptographically strong algorithm to generate pseudo-random bytes and format it as GUID v4 string

function guidv4()
{
    if (function_exists('com_create_guid') === true)
        return trim(com_create_guid(), '{}');

    $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));
}
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29
Alix Axel
8 years ago
The phunction PHP framework (http://sourceforge.net/projects/phunction/) uses the following function to generate valid version 4 UUIDs:

<?php

function GUID()
{
    if (
function_exists('com_create_guid') === true)
    {
        return
trim(com_create_guid(), '{}');
    }

    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));
}

?>

The output generated by the sprintf() and mt_rand() calls is identical to com_create_guid() results.
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17
Dave Pearson (dave at pds-uk dot com)
3 years ago
Here's my final version of a GUIDv4 function (based on others work here) that should work on all platforms and gracefully fallback to less cryptographically secure version if others are not supported...

<?php
/**
* Returns a GUIDv4 string
*
* Uses the best cryptographically secure method
* for all supported pltforms with fallback to an older,
* less secure version.
*
* @param bool $trim
* @return string
*/
function GUIDv4 ($trim = true)
{
   
// Windows
   
if (function_exists('com_create_guid') === true) {
        if (
$trim === true)
            return
trim(com_create_guid(), '{}');
        else
            return
com_create_guid();
    }

   
// OSX/Linux
   
if (function_exists('openssl_random_pseudo_bytes') === true) {
       
$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));
    }

   
// Fallback (PHP 4.2+)
   
mt_srand((double)microtime() * 10000);
   
$charid = strtolower(md5(uniqid(rand(), true)));
   
$hyphen = chr(45);                  // "-"
   
$lbrace = $trim ? "" : chr(123);    // "{"
   
$rbrace = $trim ? "" : chr(125);    // "}"
   
$guidv4 = $lbrace.
             
substr($charid08).$hyphen.
             
substr($charid84).$hyphen.
             
substr($charid, 124).$hyphen.
             
substr($charid, 164).$hyphen.
             
substr($charid, 20, 12).
             
$rbrace;
    return
$guidv4;
}
?>
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8
indrora
3 years ago
If you're going to generate random UUIDs, at least make them conform:

* The uppermost byte of the third stanza must be 4
* the uppermost byte of the fourth stanza may be any of (8 9 a b)

see also: The wikipedia page for UUIDs: https://en.wikipedia.org/wiki/Universally_unique_identifier#Version_4_.28random.29
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