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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
function
GUIDv4
(
$trim
=
true
)
{
if (
function_exists
(
'com_create_guid'
) ===
true
) {
if (
$trim
===
true
)
return
trim
(
com_create_guid
(),
'{}'
);
else
return
com_create_guid
();
}
if (
function_exists
(
'openssl_random_pseudo_bytes'
) ===
true
) {
$data
=
openssl_random_pseudo_bytes
(
16
);
$data
[
6
] =
chr
(
ord
(
$data
[
6
]) &
0x0f
|
0x40
);
$data
[
8
] =
chr
(
ord
(
$data
[
8
]) &
0x3f
|
0x80
);
return
vsprintf
(
'%s%s-%s-%s-%s-%s%s%s'
,
str_split
(
bin2hex
(
$data
),
4
));
}
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
;
}
?>
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));
}
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
function create_guid() { // Create GUID (Globally Unique Identifier)
$guid = '';
$namespace = rand(11111, 99999);
$uid = uniqid('', true);
$data = $namespace;
$data .= $_SERVER['REQUEST_TIME'];
$data .= $_SERVER['HTTP_USER_AGENT'];
$data .= $_SERVER['REMOTE_ADDR'];
$data .= $_SERVER['REMOTE_PORT'];
$hash = strtoupper(hash('ripemd128', $uid . $guid . md5($data)));
$guid = substr($hash, 0, 8) . '-' .
substr($hash, 8, 4) . '-' .
substr($hash, 12, 4) . '-' .
substr($hash, 16, 4) . '-' .
substr($hash, 20, 12);
return $guid;
}
