README

After looking at other libraries, they seem very complex for the most common use case: generating UUIDs. Now, UUIDs are quite complex in themselves, and it is easy to make mistakes so that the UUID is not truly unique. That's why I feel the library should be as simple as possible, so that it is easy to review.

Features:

UUID v4 using cryptographically strong randomness
UUID v1
COMB UUID v4 - All new UUIDs will be larger than the previous. The UUID is built from a 60 bit timestamp, a 14 bit sequence number and a 48 bit machine id. In this implementation the UUID will validate as a proper UUID v4, which means that any picky third party software which validates the UUID will treat the UUID as a compliant version 4 UUID.
Snowflake UID - 64 bit increasing ID suitable for database primary keys
Instaflake UID - a variation of the Snowflake UID
Sonyflake UID - another variation of Snowflake

This library provides two classes and has no dependencies and performs very well. The UUID v4 is cryptographic random (via random_bytes()), while UUID v1 tries to find the MAC address or another unique machine ID. To reduce the risk of collisions, the process id is used to to reduce the chance of a single machine generating two identical IDs.

Benchmarks

First UUID is generated almost as quickly as the native PECL extension

[Edit](https://quickchart.io/chart-maker/edit/zm-ba284464-1ba4-4795-a7e8-dcf8f00d1e71)

Faster then the native PECL extension for many UUIDs.

[Edit](https://quickchart.io/chart-maker/edit/zm-42160b97-4a31-4a17-b591-98676a688b09)

Summary

See the BENCHMARKS.md file for full details. The noteworthy details are:

Less then 1 ms to generate the first UUID, 10.5 milliseconds faster than ramsey/uuid for UUID v1 and 3.9 ms faster for UUID v4.
Overhead is related to loading of the source files.

Are these UUIDs truly unique?

UUID(4)

The random UUID(4) generated by this library are industrial strength, directly using the entropy from the operating system via the random_bytes() function.

UUID(1)

The time and place based UUID(1) algorithm was implemented while taking into account bug reports and experiences made in other libraries. Subtle issues that can arise is related to forking of the process and The algorithm for building the bytes is an exact port of the C code provided in appendix A of the RFC 4122.

However, the microtime(true) function in PHP does not provide an accurate enough time resolution,

A lot of effort was put into defining the UUID standard, and a they are considered to be unique for all practical purposes.

UUID v4 is the simplest to use, but they require 16 bytes of storage each. They need no configuration, and they can be generated very quickly. If all companies in the world generate a total of 1 billion UIDs every second, the first collision is expected to happen after about 85 years. After those 85 years, most of these UUIDs will have vanished anyway.

Snowflake ID are only 8 bytes (64 bits) and can safely be be used inside your own databases. They were invented by Twitter and is used to generate unique IDs for tweets, users, things, images and so on. To ensure uniqueness, you may configure a unique machineId, but the library will automatically pick an available machine id from the operating system if you don't.

UUID v1 is a "coordinate" using the clock and a unique machine id derived from the mac address or another unique 48 bit machine identifier. They are also automatically configured in this library.

Warning

Please run some tests in your environment before using this library. Particularly, ensure that the server has enough entropy available if you're using UUID version 4. Entropy is random numbers generated from network noise and other sources.

UUIDs version 4 are considered production ready, but the other IDs need some more scrutiny before we can declare them production ready. Please let me know if you spot any problems.

Quick Start

If you're not using a service container, the quickest way to begin is by using the function Charm\Id::make(). The returned value will be a cryptographically random 128 bit value in UUID v4 form (XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX).

Installation

As with most PHP packages, install composer and run

# composer require charm/uuid

Alternatively you can of course clone the repository from https://github.com/charm-php/uuid and include the ./autoload.php file we've provided.

UUID v4

This is the fastest and easiest to use, as it has no configuration options. The probability of a collission is microscopic. The number of different combinations is approximately 5,3169e+36.

If collisions happen, it is because of bugs in the generator. The ramsay If you've heard that collisions happen, you can be quite certain that the collision happened because of using an inferior random number generator.

Quotes from around the web:

| If you generate 103 trillion UUID v4, the probability of a collision is about 1 in a billion.

| If you have a database of 1 petabyte of UUIDs, the probability of a single collision is | one in 50 billion.

| If you generate 8 billion UUIDs per second,

<?php
echo Charm\Id::make();
// "47e3c427-3f82-4dc7-a6ca-c83561a9cdfb"

UUID v1

This UUID is guaranteed to be unique, provided you have a unique machine ID - for example using a MAC address.

<?php
echo Charm\Id::v1();
// "c85fb57a-f391-11eb-bb00-0242ee781401"

<?php
/**
 * UUID v4
 *
 * An ID that can be shared with others, and you should never see a collision.
 */
$uniqueId = Charm\Id::make();               // returns a 36 char string
// "47e3c427-3f82-4dc7-a6ca-c83561a9cdfb"

/**
 * Snowflake, by Twitter
 *
 * A 64 bit integer which can be considered unique within your organization, built from
 * a timestamp, a machine id and a sequence number.
 */
$snowflakeId = Charm\Id::snowflake(); // returns 64 bit int value
// 262805082062461697

Service Object API

<?php
use Charm\Util\IdFactory;

$idGenerator = new IdFactory(IdFactory::TYPE_UUID_V1, [
    /**
     * If you specify a machine id here, no effort is needed to retrieve a machine id.
     * The value should be globally unique for UUID V1, or unique for the organization
     * for snowflake/instaflake/sonyflake type IDs.
     */
    'machineId' => null,

    /**
     * The sequence number is a number which is supposed to ensure that we don't generate
     * two IDs on the same computer within the same time interval. The default value is derived
     * from `getmypid()` which should cause diffent workers to start on a different sequence
     * number.
     */
    'initialSequenceNumber' => null,

    /**
     * The epoch for the snowflake and derivatives ID generators is a unix
     * timestamp.
     */
    'epoch' => strtotime('2019-01-01 00:00:00'),

    /**
     * Allow fetching the computers mac address for machine id?
     */
    'allowMacAddress' => true,

    /**
     * Allow using the Kubernetes hostname UID part for machine id?
     */
    'allowKubernetesId' => true,

    /**
     * Allow unique machine ID from /var/lib/dbus/machine-id or on Windows, the registry entry in 
     * 'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Cryptography\MachineGuid'?
     */
    'allowMachineId' => true,

    /**
     * You can provide a custom function that provides a unique ID for the machine. The function
     * must return a positive integer or NULL.
     */
    'customMachineIdFunction' => null,
]);

// Generate a new ID. The type of ID is determined by the `$type` specified in the constructor.
$idGenerator(); // c85fb57a-f391-11eb-bb00-0242ee781401

Static API

<?php
use Charm\Id;
use Charm\Util\IdFactory;

// Optionally configure the library before generating any IDs.
Id::configure(IdFactory::TYPE_UUID_V4, [ /* options, see above */);

// Generate the default ID type
Id::make();
// 47e3c427-3f82-4dc7-a6ca-c83561a9cdfb

// Or use any of the other factory methods to create a particular type of ID

Charm\Id::uuid1();
// c85fb57a-f391-11eb-bb00-0242ee781401

Charm\Id::uuid4();
// 47e3c427-3f82-4dc7-a6ca-c83561a9cdfb

Charm\Id::comb();
// 061089ba-be18-475b-90ed-0242ee781401

Charm\Id::snowflake();
// 262805082062461697

Charm\Id::instaflake();
// 262805082067699458

Charm\Id::sonyflake();
// 33064438777189377

Configuration:

Configuration is done via the IdFactory constructor, or the Id::configure() method. For up-to-date configuration options, see the IdFactory source file.

Comparison:

UUID v1 provides an 128 bit RFC4122 compliant UUID version 1 variant 1. It is designed to be globally unique for any datacenter and computer, always. It uses 48 bits to uniquely identify the computer it runs on, and a 60 bit timestamp in 100 nanosecond increments since 15th October 1582. The probability for a collision is extremely small.
UUID v4 provides an 128 bit RFC4122 compliant UUID v4 variant 1 (also aka GUID). It is built from a very large 122 bit random number. The generator uses a random_bytes() which consumes random numbers which are considered cryptographically secure.
COMB UUID camouflages as a 128 bit RFC4122 compliant UUID v4, but it is built using the same principles as UUID v1: 60 bit timestamp, 14 bit sequence ID and 48 bit machine ID in a sorted order.
Snowflake is a 64 bit integer, which is suitable for storing in databases and is able to guarantee unique IDs across data centers and servers - provided that the machine ID is unique.
Instaflake and Sonyflake are variations of Snowflake, with different priorities with regard to timestamp resolution and number of machines.

Snowflake and variants are usually sufficient for any internal ID scheme up to Twitter or Instagram scale. UUIDs are by many considered to be too large to be used extensively internally in a database - but are very useful to generate unique IDs for APIs or for allowing external clients to generate IDs offline.

charm / uuid

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