The ClassLoader ComponentEdit this page
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Read the updated version of this page for Symfony 6.0 (the current stable version).
The ClassLoader component provides tools to autoload your classes and cache their locations for performance.
The ClassLoader component was deprecated in Symfony 3.3 and it will be removed in 4.0. As an alternative, use any of the class loading optimizations provided by Composer.
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:
- The PSR-0 Class Loader: loads classes that follow the PSR-0 class naming standard;
- The PSR-4 Class Loader: loads classes that follow the PSR-4 class naming standard;
- MapClassLoader: 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 to cache the results of a class loader.
You can install the component in 2 different ways:
- Install it via Composer (
- Use the official Git repository (https://github.com/symfony/class-loader).
Then, require the
vendor/autoload.php file to enable the autoloading mechanism
provided by Composer. Otherwise, your application won't be able to find the classes
of this Symfony component.