Pure PHP UUID generator

demo.php

<?php

// Usage
include 'UUID.php';

// Named-based UUID.
$v3uuid = UUID::v3('1546058f-5a25-4334-85ae-e68f2a44bbaf', 'SomeRandomString');
$v5uuid = UUID::v5('1546058f-5a25-4334-85ae-e68f2a44bbaf', 'SomeRandomString');

// Pseudo-random UUID
$v4uuid = UUID::v4();

?>

UUID.php

<?php
/**
 * UUID class
 *
 * The following class generates VALID RFC 4122 COMPLIANT
 * Universally Unique IDentifiers (UUID) version 3, 4 and 5.
 *
 * UUIDs generated validates using OSSP UUID Tool, and output
 * for named-based UUIDs are exactly the same. This is a pure
 * PHP implementation.
 *
 * @author Andrew Moore
 * @link http://www.php.net/manual/en/function.uniqid.php#94959
 */
class UUID
{
	/**
	 * Generate v3 UUID
	 *
	 * Version 3 UUIDs are named based. They require a namespace (another 
	 * valid UUID) and a value (the name). Given the same namespace and 
	 * name, the output is always the same.
	 * 
	 * @param	uuid	$namespace
	 * @param	string	$name
	 */
	public static function v3($namespace, $name)
	{
		if(!self::is_valid($namespace)) return false;

		// Get hexadecimal components of namespace
		$nhex = str_replace(array('-','{','}'), '', $namespace);

		// Binary Value
		$nstr = '';

		// Convert Namespace UUID to bits
		for($i = 0; $i < strlen($nhex); $i+=2) 
		{
			$nstr .= chr(hexdec($nhex[$i].$nhex[$i+1]));
		}

		// Calculate hash value
		$hash = md5($nstr . $name);

		return sprintf('%08s-%04s-%04x-%04x-%12s',

		// 32 bits for "time_low"
		substr($hash, 0, 8),

		// 16 bits for "time_mid"
		substr($hash, 8, 4),

		// 16 bits for "time_hi_and_version",
		// four most significant bits holds version number 3
		(hexdec(substr($hash, 12, 4)) & 0x0fff) | 0x3000,

		// 16 bits, 8 bits for "clk_seq_hi_res",
		// 8 bits for "clk_seq_low",
		// two most significant bits holds zero and one for variant DCE1.1
		(hexdec(substr($hash, 16, 4)) & 0x3fff) | 0x8000,

		// 48 bits for "node"
		substr($hash, 20, 12)
		);
	}

	/**
	 * 
	 * Generate v4 UUID
	 * 
	 * Version 4 UUIDs are pseudo-random.
	 */
	public static function v4() 
	{
		return sprintf('%04x%04x-%04x-%04x-%04x-%04x%04x%04x',

		// 32 bits for "time_low"
		mt_rand(0, 0xffff), mt_rand(0, 0xffff),

		// 16 bits for "time_mid"
		mt_rand(0, 0xffff),

		// 16 bits for "time_hi_and_version",
		// four most significant bits holds version number 4
		mt_rand(0, 0x0fff) | 0x4000,

		// 16 bits, 8 bits for "clk_seq_hi_res",
		// 8 bits for "clk_seq_low",
		// two most significant bits holds zero and one for variant DCE1.1
		mt_rand(0, 0x3fff) | 0x8000,

		// 48 bits for "node"
		mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
		);
	}

	/**
	 * Generate v5 UUID
	 * 
	 * Version 5 UUIDs are named based. They require a namespace (another 
	 * valid UUID) and a value (the name). Given the same namespace and 
	 * name, the output is always the same.
	 * 
	 * @param	uuid	$namespace
	 * @param	string	$name
	 */
	public static function v5($namespace, $name) 
	{
		if(!self::is_valid($namespace)) return false;

		// Get hexadecimal components of namespace
		$nhex = str_replace(array('-','{','}'), '', $namespace);

		// Binary Value
		$nstr = '';

		// Convert Namespace UUID to bits
		for($i = 0; $i < strlen($nhex); $i+=2) 
		{
			$nstr .= chr(hexdec($nhex[$i].$nhex[$i+1]));
		}

		// Calculate hash value
		$hash = sha1($nstr . $name);

		return sprintf('%08s-%04s-%04x-%04x-%12s',

		// 32 bits for "time_low"
		substr($hash, 0, 8),

		// 16 bits for "time_mid"
		substr($hash, 8, 4),

		// 16 bits for "time_hi_and_version",
		// four most significant bits holds version number 5
		(hexdec(substr($hash, 12, 4)) & 0x0fff) | 0x5000,

		// 16 bits, 8 bits for "clk_seq_hi_res",
		// 8 bits for "clk_seq_low",
		// two most significant bits holds zero and one for variant DCE1.1
		(hexdec(substr($hash, 16, 4)) & 0x3fff) | 0x8000,

		// 48 bits for "node"
		substr($hash, 20, 12)
		);
	}

	public static function is_valid($uuid) {
		return preg_match('/^\{?[0-9a-f]{8}\-?[0-9a-f]{4}\-?[0-9a-f]{4}\-?'.
                      '[0-9a-f]{4}\-?[0-9a-f]{12}\}?$/i', $uuid) === 1;
	}
}
?>

For random UUIDs without using mt_rand(), still simple enough to hack to your needs, I offer this Gist.

I needed UUIDs recently and found the same comment from PHP documentation and made my implementation based on that. If anybody wants to check out my version, you can find it from https://github.com/oittaa/uuid-php/. It's basically a bit cleaned up version from this one, except it tries to use random_bytes and openssl_random_pseudo_bytes for version 4 UUID instead of mt_rand.

https://gist.github.com/FlorinAsavoaie/525c98d71d719147aa18c931c8336d94

Please update from here. Way more efficient and better randomness for v4.

Added time-based v1 uuid generation.

Well, you can consider

1. This library, easy to use if you are using PHP 7!
2. If you are using PHP 8 consider using UID from Infocyph!