Horde Autoloader

PSR-0 and PSR-4 compliant autoloader for PHP 8.0+

Why Horde Autoloader?

Horde Autoloader predates PSR-0 and is mostly maintained for legacy and educational purposes. Horde itself primarily uses composer autoloader as does everybody else. Remaining calls into Horde Autoloader from the Horde Framework are going to be removed step by step.

If you need a config-is-code, self-contained, PSR-0 capable autoloader and composer autoloader is not an option, give it a try. Your reasons are yours.

Features

• PSR-4 Support - Autoloading with namespaces
• PSR-0 Support - PEAR-style autoloading without namespaces, underscores as subdir separators.
• Classpath Mappers - Application, Prefix, PrefixString patterns
• PHP 8.0+ - Full type safety and modern features
• LIFO Ordering - Last-added mapper searched first
• Callback Support - Execute code after class loads
• No Dependencies - Self-contained library

Quick Start

Modern (PSR-4 with PSR-0 support)

// Autoloader bootstraps itself - require files explicitly
require_once __DIR__ . '/vendor/horde/autoloader/src/Autoloader.php';
require_once __DIR__ . '/vendor/horde/autoloader/src/ClassPathMapper/Psr4.php';

use Horde\Autoloader\Autoloader;
use Horde\Autoloader\ClassPathMapper\Psr4;

$autoloader = new Autoloader();
$psr4 = new Psr4(enablePsr0Fallback: false);
$psr4->addNamespace('Acme\Log', __DIR__ . '/vendor/acme/log/src');
$autoloader->addClassPathMapper($psr4);
$autoloader->registerAutoloader();

Legacy (PSR-0 based PSR-0)

// Autoloader bootstraps itself - require files explicitly
require_once __DIR__ . '/vendor/horde/autoloader/lib/Horde/Autoloader.php';

$autoloader = new Horde_Autoloader();
$autoloader->addClassPathMapper(
    new Horde_Autoloader_ClassPathMapper_Default(__DIR__ . '/lib')
);
$autoloader->registerAutoloader();

Installation

composer require horde/autoloader

Documentation

• Examples (Legacy PSR-0) - PSR-0 usage examples
• Examples (Modern) - PSR-4 and modern features
• Upgrading Guide - Migration from PSR-0 to PSR-4
• Changelog - Version history

Requirements

• PHP 8.0 or higher

Key Differences: PSR-0 vs PSR-4

Feature	PSR-0	PSR-4
Underscores	Converted to /	Preserved as-is
Namespace mapping	Simple path	Prefix → base directory
Top-level classes	Allowed	Rejected (requires namespace)
Multiple base dirs	No	Yes

PSR-0 Example

// Class: Vendor_Package_Class_Name
// Maps to: vendor/Vendor/Package/Class/Name.php

PSR-4 Example

// Prefix: Vendor\Package → /vendor/package/src
// Class: \Vendor\Package\Class_Name
// Maps to: /vendor/package/src/Class_Name.php (underscore preserved!)

Available Mappers

Modern (src/)

• Psr4 - PSR-4 compliant autoloader with namespace prefix mapping
• DefaultMapper - PSR-0 compliant mapper (underscores → directories)
• Application - Application-specific MVC pattern mapper
• Prefix - Regex-based prefix matching
• PrefixString - Fast case-insensitive string prefix matching

Legacy (lib/)

• Horde_Autoloader_ClassPathMapper_Default - PSR-0 mapper
• Horde_Autoloader_ClassPathMapper_Application - Application mapper
• Horde_Autoloader_ClassPathMapper_Prefix - Regex prefix
• Horde_Autoloader_ClassPathMapper_PrefixString - String prefix

Testing

# Run all tests
phpunit

# Run specific test suites
phpunit --testsuite unit        # Legacy PSR-0 tests
phpunit --testsuite modern      # Modern PSR-4 tests
phpunit --testsuite integration # Real file loading tests

License

LGPL-2.1-only

Links

• Homepage: https://www.horde.org/libraries/Horde_Autoloader
• Repository: https://github.com/horde/Autoloader
• PSR-4 Specification: https://www.php-fig.org/psr/psr-4/
• PSR-0 Specification: https://www.php-fig.org/psr/psr-0/

Credits

• Authors: Bob Mckee, Chuck Hagenbuch
• Maintainers: Jan Schneider, Ralf Lang