com_create_guid()

(PHP 5, PHP 7)

Generate a globally unique identifier(GUID)

说明

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.

返回值

Returns the GUID as a string.

参见

• uuid_create() in the PECL uuid extension

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.

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));
}

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 = $lbrace.
       substr($charid, 0, 8).$hyphen.
       substr($charid, 8, 4).$hyphen.
       substr($charid, 12, 4).$hyphen.
       substr($charid, 16, 4).$hyphen.
       substr($charid, 20, 12).
       $rbrace;
  return $guidv4;
}
?>

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

I implemented a com_create_guid implementation for systems that do not support it as a Composer package in order to keep it separated from my applications 
https://github.com/rogervila/com_create_guid