A PHP implementation of collision-resistant identifiers that are secure, URL-safe, and horizontally scalable. Perfect for distributed systems where unique identifiers need to be generated across multiple machines without coordination.

CUID2 (Collision-resistant Unique Identifier, version 2) is a modern approach to generating unique identifiers that addresses common issues with UUIDs and other identification systems. This PHP implementation provides:

• Collision Resistance: Uses cryptographic hashing (SHA3-512) combined with timestamps, counters, and fingerprints to ensure uniqueness
• Horizontal Scalability: Safe to use across multiple machines and processes without coordination
• Security: Employs cryptographically secure random generation and hashing
• URL-Safe: Uses base36 encoding (0-9, a-z) with lowercase letters only
• Sortability: Incorporates timestamps for chronological ordering
• Configurable Length: Supports identifier lengths from 4 to 32 characters (default 24)

You can read more about CUIDs from the official project website.

Each CUID2 identifier is composed of several components that are combined and hashed to ensure uniqueness:

[prefix][hash]

• Prefix (1 character): Random lowercase letter (a-z)
• Hash (remaining characters): Base36-encoded SHA3-512 hash of combined components

1. Prefix: Random lowercase letter for additional entropy
2. Timestamp: Current time in milliseconds for sortability
3. Counter: Monotonically increasing value (prevents collisions for rapid generation)
4. Fingerprint: Machine/process identifier (hostname + PID + environment)
5. Random Data: Cryptographically secure random bytes
6. Hashing: All components are combined and hashed using SHA3-512
7. Encoding: Hash is converted from base16 to base36
8. Truncation: Result is trimmed to requested length (minus prefix)

Example output: p6p168tx2rxtgyehd3p2wz04

This architecture ensures that even if multiple processes generate CUIDs simultaneously, the combination of timestamp, counter, fingerprint, and random data prevents collisions.

Install visus/cuid2 via Composer:

composer require visus/cuid2

Requirements:

• PHP 8.2 or higher
• SHA3-512 hashing algorithm support (typically available in PHP 7.1+)

Recommended:

• GMP extension for optimal performance (60-300x faster base conversion)

<?php
require_once 'vendor/autoload.php';
use Visus\Cuid2\Cuid2;
// Generate with default length of 24 characters
$cuid = new Cuid2();
// Implicit casting
echo $cuid; // p6p168tx2rxtgyehd3p2wz04
// Explicit casting
echo $cuid->toString(); // p6p168tx2rxtgyehd3p2wz04
// Generate with custom length (4-32 characters)
$shortCuid = new Cuid2(10);
echo $shortCuid; // a1ao2r0lve

<?php
require_once 'vendor/autoload.php';
use Visus\Cuid2\Cuid2;
// Generate with default length of 24 characters
$cuid = Cuid2::generate();
// Implicit casting
echo $cuid; // zbc8kp9qqoh3pvseey6m7nrq
// Explicit casting
echo $cuid->toString(); // zbc8kp9qqoh3pvseey6m7nrq
// Generate with custom length (4-32 characters)
$shortCuid = Cuid2::generate(10);
echo $shortCuid; // rywe9nkxrx

The isValid() method checks if a string follows the CUID2 format.

<?php
require_once 'vendor/autoload.php';
use Visus\Cuid2\Cuid2;
// Validate format
Cuid2::isValid('p6p168tx2rxtgyehd3p2wz04'); // true
Cuid2::isValid('invalid-cuid'); // false
// Validate with expected length
Cuid2::isValid('a1ao2r0lve', expectedLength: 10); // true
Cuid2::isValid('a1ao2r0lve', expectedLength: 24); // false

This library uses base conversion (base16 to base36) as part of the CUID2 generation process. For optimal performance, it is strongly recommended to install or enable the GMP extension.

Performance Comparison (based on benchmarks):

Key Takeaways:

• GMP provides 60-300x faster base conversion
• Larger hashes benefit more from GMP (CUID2 uses SHA3-512, the largest case)
• Without GMP, the library falls back to a pure PHP implementation
• Both implementations produce identical results

Installation:

# Ubuntu/Debian
sudo apt-get install php-gmp
# Fedora/RHEL/CentOS/AlmaLinux/Rocky Linux
sudo dnf install php-gmp
# Or on older systems: sudo yum install php-gmp
# FreeBSD
sudo pkg install php-gmp
# Or via ports: cd /usr/ports/math/php-gmp && make install clean
# NetBSD
sudo pkgin install php-gmp
# Or via pkgsrc: cd /usr/pkgsrc/math/php-gmp && make install
# OpenBSD
sudo pkg_add php-gmp
# Or via ports: cd /usr/ports/math/php-gmp && make install
# macOS (via Homebrew)
brew install gmp
pecl install gmp
# Windows
# GMP is often bundled with PHP installations
# Enable in php.ini by uncommenting:
extension=gmp
# If not bundled, download from PECL or use package manager:
# Via Chocolatey: choco install php-gmp

Run php -m | grep gmp (Unix) or php -m | findstr gmp (Windows) to verify the extension is loaded.

Contributions are welcome! Please see CONTRIBUTING.md for detailed guidelines on:

• Setting up your development environment
• Running tests and code quality checks
• Coding standards and conventions
• Submitting pull requests

This project follows Conventional Commits and maintains 100% code coverage.