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ClassLoader Component

ClassLoader loads your project classes automatically if they follow some standard PHP conventions.

The Universal ClassLoader is able to autoload classes that implement the PSR-0 standard or the PEAR naming convention.

First, register the autoloader:

require_once __DIR__.'/src/Symfony/Component/ClassLoader/UniversalClassLoader.php';

use Symfony\Component\ClassLoader\UniversalClassLoader;

$loader = new UniversalClassLoader();

Then, register some namespaces with the registerNamespace() method:

$loader->registerNamespace('Symfony', __DIR__.'/src');
$loader->registerNamespace('Monolog', __DIR__.'/vendor/monolog/src');

The registerNamespace() method takes a namespace prefix and a path where to look for the classes as arguments.

You can also register a sub-namespaces:

$loader->registerNamespace('Doctrine\\Common', __DIR__.'/vendor/doctrine-common/lib');

The order of registration is significant and the first registered namespace takes precedence over later registered one.

You can also register more than one path for a given namespace:

$loader->registerNamespace('Symfony', array(__DIR__.'/src', __DIR__.'/symfony/src'));

Alternatively, you can use the registerNamespaces() method to register more than one namespace at once:

    'Symfony'          => array(__DIR__.'/src', __DIR__.'/symfony/src'),
    'Doctrine\\Common' => __DIR__.'/vendor/doctrine-common/lib',
    'Doctrine'         => __DIR__.'/vendor/doctrine/lib',
    'Monolog'          => __DIR__.'/vendor/monolog/src',

For better performance, you can use the APC based version of the universal class loader:

require_once __DIR__.'/src/Symfony/Component/ClassLoader/UniversalClassLoader.php';
require_once __DIR__.'/src/Symfony/Component/ClassLoader/ApcUniversalClassLoader.php';

use Symfony\Component\ClassLoader\ApcUniversalClassLoader;

$loader = new ApcUniversalClassLoader('apc.prefix.');

Furthermore, the component provides tools to aggregate classes into a single file, which is especially useful to improve performance on servers that do not provide byte caches.