##Synopsis

Paulyg\Autoloader is about the smallest and simplest PHP class autoloader you can imagine. It loads classes following both the established and popular PSR-0 standard and the recently ratified PSR-4 standard. It uses PHP's internal SPL stack to keep track of prefix-directory mappings rather than doing it in userland code.

##Motivation

There are plenty of autoloading libraries and components already for PHP. So why would I want to write my own? My original motivation was to eliminate the many empty directories that are a consequence of the PSR-0 directory structure. This gets exasperated if you are using Composer to manage libraries. Here is an example, pretend we are using Zend\Feed, which pulls in Zend\Stdlib and Zend\Escaper.

/path/to/project/vendor/zendframework/zend-feed/Zend/Feed/
/path/to/project/vendor/zendframework/zend-stdlib/Zend/Stdlib/
/path/to/project/vendor/zendframework/zend-escaper/Zend/Escaper/
                              |             |       |     |
                              |             |       |     `-- Finally code here!
                              |             |       |
                              |             |       `-- No code in this dir
                              |             |
                              |             `-- No code in this dir
                              |
                              `-- No code in this dir

I was constantly traversing those empty directories in my own code and in looking at library code. Composer enforces the first two directories, e.g. zendframework/zend-blah, as part of its own namespacing scheme. But at least I could squash the other two. I called this aliasing, and the first version of this autoloader had a method called addAlias(). Later I saw the PSR-4 proposal from PHP-FIG that is essentially the same idea. So that method got renamed to addPsr4(), even though PSR-4 has still not been ratified. Disclaimer: I have no affiliation with PHP-FIG.

The PSR-4 autoloading standard allows you to stucture library code like so.

/path/to/project/vendor/zf/zend-feed/Reader.php <- Class: Zend\Feed\Reader
                                     Writer.php <- Class: Zend\Feed\Writer
                                     AbstractEntry.php <- Class: Zend\Feed\AbstractEntry

And autoload them like so.

<?php
use Paulyg\Autoloader;
Autoloader::addPsr4('Zend\Feed', '/path/to/project/zf/zend-feed');
$reader = new \Zend\Feed\Reader();

A secondary motivation was some postings I saw in the PHPUnit issues on Github, re Sebastian Bergmann not wanting to incude a PSR-0 autoloader in PHPUnit. His main beef was that all the current PSR-0 autoloaders maintain the map of namespace/class prefixes to directories in userspace PHP arrays rather than in the spl_autoloader stack where it is managed by more efficient compiled C code. I believe Sebastian actually prefers classmaps but I took the point about putting the spl_autoloader stack to better use with this library.

Installation

The autoloader is just one small class file and I don't expect it to change much so I recommend just downloading it from Github using the raw feature.

$ wget https://github.com/paulyg/autoloader/raw/master/src/Paulyg/Autoloader.php

Or you could use Composer. Add the following to your project's composer.json file:

{
    "require": {
        "paulyg/autoloader": "dev-master"
    }
}

Or clone the Git repo.

$ git clone https://github.com/paulyg/autoloader

API

3 simple methods. All methods work both staticlly or called from an instance.

1. addPsr0($prefix, $dir, $prepend = false)
2. addPsr4($prefix, $dir, $prepend = false)
3. remove($prefix, $dir)

Examples

PSR-0

Basic loading of classes with namespace and PSR-0 directory structure.

<?php
use Paulyg\Autoloader;
Autoloader::addPsr0('Symfony', '/path/to/project/vendor/symfony/src');
$collection = new Symfony\Component\Routing\RouteCollection();

Loads from /path/to/project/vendor/symfony/src/Symfony/Component/Routing/RouteCollection.php

Leading (root) namespace separators are stripped. These two are equivalent.

<?php
use Paulyg\Autoloader;
Autoloader::addPsr0('Silex', '/path/to/project/vendor/silex/silex/src');
Autoloader::addPsr0('\Silex', '/path/to/project/vendor/silex/silex/src');

Trailing namespace separators are honored. This is useful when you have namespaced code and non-namespaced code that share the same prefix. This example also illustrates using from an instance vs the static method calls.

<?php
$autoloader = new Paulyg\Autoloader();
$autoloader->addPsr0('Zend\\', '/path/to/project/vendor/zf2/library');
$reader = new Zend\Feed\Reader(); // <- will load class
$writer = new Zend_Feed_Writer(); // <- will not load class

Load PEAR/Zend/Horde style classes. Note they are still PSR-0 compliant even though many other libraries have a separate method for namespaced and non-namespaced classes.

<?php
use Paulyg\Autoloader;
Autoloader::addPsr0('Zend', '/path/to/project/vendor/zf1/library');
$writer = new Zend_Feed_Writer(); // <- Now works

Works with trailing underscore as well.

<?php
use Paulyg\Autoloader;
Autoloader::addPsr0('Zend_', '/path/to/project/vendor/zf1/library');
$writer = new Zend_Feed_Writer(); // <- Still works
$fooBar = new ZendFooBar(); // <- Nothing found

PSR-4

Basic loading of classes with namespace and PSR-4 directory structure.

<?php
use Paulyg\Autoloader;
Autoloader::addPsr4('Symfony\Component\Routing', '/path/to/project/vendor/symfony/routing/');
$collection = new Symfony\Component\Routing\RouteCollection();

Loads from /path/to/project/vendor/symfony/routing/RouteCollection.php

Leading (root) namespace separators are again stripped. These two are equivalent.

<?php
use Paulyg\Autoloader;
Autoloader::addPsr4('Zend\Db', '/path/to/project/vendor/zendframework/zend-db/');
Autoloader::addPsr4('\Zend\Db', '/path/to/project/vendor/zendframework/zend-db/');

Trailing namespace separators are honored the same way as PSR-0. This example also illustrates using from an instance vs the static method calls.

<?php
$autoloader = new Paulyg\Autoloader();
$autoloader->addPsr4('Zend\Feed', '/path/to/project/vendor/zendframework/zend-feed/');
$reader = new Zend\Feed\Reader(); // <- will load class
$writer = new Zend_Feed_Writer(); // <- will not load class

Tests

Paulyg\Autoloader comes with a full set of tests, written with PHPUnit. To run the tests yourself run the following command from the test directory.

$ phpunit "Paulyg\AutoloaderTest"

License

Paulyg\Autoloader is licensed using the MIT license.