com_create_guid()

(PHP 5, PHP 7)

Generate a globally unique identifier(GUID)

说明

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:

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... 

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

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