class_loader.rst

.. index::
    single: Components; ClassLoader

The ClassLoader Component

The ClassLoader component provides tools to autoload your classes and cache their locations for performance.

Caution!

The ClassLoader component was deprecated in Symfony 3.3 and it will be removed in 4.0. As an alternative, use Composer's class loading mechanism.

Usage

Whenever you reference a class that has not been required or included yet, PHP uses the autoloading mechanism to delegate the loading of a file defining the class. Symfony provides three autoloaders, which are able to load your classes:

• :doc:`/components/class_loader/class_loader`: loads classes that follow the PSR-0 class naming standard;
• :doc:`/components/class_loader/psr4_class_loader`: loads classes that follow the PSR-4 class naming standard;
• :doc:`/components/class_loader/map_class_loader`: loads classes using a static map from class name to file path.

Additionally, the Symfony ClassLoader component ships with a wrapper class which makes it possible :doc:`to cache the results of a class loader </components/class_loader/cache_class_loader>`.

When using the :doc:`Debug component </components/debug>`, you can also use a special :ref:`DebugClassLoader <component-debug-class-loader>` that eases debugging by throwing more helpful exceptions when a class could not be found by a class loader.

Installation

You can install the component in 2 different ways:

• :doc:`Install it via Composer </components/using_components>` (symfony/class-loader on Packagist);
• Use the official Git repository (https://github.com/symfony/class-loader).

Learn More

.. toctree::
    :glob:
    :maxdepth: 1

    class_loader/class_loader
    class_loader/*