The Class Map Generator

The Class Map Generator

Loading a class usually is an easy task given the PSR-0 and PSR-4 standards. Thanks to the Symfony ClassLoader component or the autoloading mechanism provided by Composer, you don't have to map your class names to actual PHP files manually. Nowadays, PHP libraries usually come with autoloading support through Composer.

But from time to time you may have to use a third-party library that comes without any autoloading support and therefore forces you to load each class manually. For example, imagine a library with the following directory structure:

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library/
├── bar/
│   ├── baz/
│   │   └── Boo.php
│   └── Foo.php
└── foo/
    ├── bar/
    │   └── Foo.php
    └── Bar.php

These files contain the following classes:

File Class Name
library/bar/baz/Boo.php Acme\Bar\Baz
library/bar/Foo.php Acme\Bar
library/foo/bar/Foo.php Acme\Foo\Bar
library/foo/Bar.php Acme\Foo

To make your life easier, the ClassLoader component comes with a ClassMapGenerator class that makes it possible to create a map of class names to files.

Generating a Class Map

To generate the class map, simply pass the root directory of your class files to the createMap() method:

use Symfony\Component\ClassLoader\ClassMapGenerator;

var_dump(ClassMapGenerator::createMap(__DIR__.'/library'));

Given the files and class from the table above, you should see an output like this:

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Array
(
    [Acme\Foo] => /var/www/library/foo/Bar.php
    [Acme\Foo\Bar] => /var/www/library/foo/bar/Foo.php
    [Acme\Bar\Baz] => /var/www/library/bar/baz/Boo.php
    [Acme\Bar] => /var/www/library/bar/Foo.php
)

Dumping the Class Map

Writing the class map to the console output is not really sufficient when it comes to autoloading. Luckily, the ClassMapGenerator provides the dump() method to save the generated class map to the filesystem:

use Symfony\Component\ClassLoader\ClassMapGenerator;

ClassMapGenerator::dump(__DIR__.'/library', __DIR__.'/class_map.php');

This call to dump() generates the class map and writes it to the class_map.php file in the same directory with the following contents:

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<?php return array (
'Acme\\Foo' => '/var/www/library/foo/Bar.php',
'Acme\\Foo\\Bar' => '/var/www/library/foo/bar/Foo.php',
'Acme\\Bar\\Baz' => '/var/www/library/bar/baz/Boo.php',
'Acme\\Bar' => '/var/www/library/bar/Foo.php',
);

Instead of loading each file manually, you'll only have to register the generated class map with, for example, the MapClassLoader:

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use Symfony\Component\ClassLoader\MapClassLoader;

$mapping = include __DIR__.'/class_map.php';
$loader = new MapClassLoader($mapping);
$loader->register();

// you can now use the classes:
use Acme\Foo;

$foo = new Foo();

// ...

Note

The example assumes that you already have autoloading working (e.g. through Composer or one of the other class loaders from the ClassLoader component.

Besides dumping the class map for one directory, you can also pass an array of directories for which to generate the class map (the result actually is the same as in the example above):

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use Symfony\Component\ClassLoader\ClassMapGenerator;

ClassMapGenerator::dump(
    array(__DIR__.'/library/bar', __DIR__.'/library/foo'),
    __DIR__.'/class_map.php'
);

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.