By default, the Symfony Standard Edition uses Composer's autoloader

in the `autoload.php`_ file. This autoloader is easy to use, as it will

Caching the Autoloader with APC

Another solution is to cache the location of each class after it's located

the first time. Symfony comes with a class - :class:`Symfony\\Component\\ClassLoader\\ApcClassLoader` -

that does exactly this. To use it, just adapt your front controller file.

If you're using the Standard Distribution, make the following changes::

For more details, see :doc:`/components/class_loader/cache_class_loader`.

.. note::

When using the APC autoloader, if you add new classes, they will be found

automatically and everything will work the same as before (i.e. no

reason to "clear" the cache). However, if you change the location of a

particular namespace or prefix, you'll need to flush your APC cache. Otherwise,

the autoloader will still be looking at the old location for all classes

inside that namespace.

.. index::

single: Performance; Bootstrap files

Use Bootstrap Files

To ensure optimal flexibility and code reuse, Symfony applications leverage

a variety of classes and 3rd party components. But loading all of these classes

from separate files on each request can result in some overhead. To reduce

this overhead, the Symfony Standard Edition provides a script to generate

a so-called `bootstrap file`_, consisting of multiple classes definitions

in a single file. By including this file (which contains a copy of many of

the core classes), Symfony no longer needs to include any of the source files

containing those classes. This will reduce disc IO quite a bit.

If you're using the Symfony Standard Edition, then you're probably already

using the bootstrap file. To be sure, open your front controller (usually

``app.php``) and check to make sure that the following line exists::

Note that there are two disadvantages when using a bootstrap file:

* the file needs to be regenerated whenever any of the original sources change

(i.e. when you update the Symfony source or vendor libraries);

* when debugging, one will need to place break points inside the bootstrap file.

If you're using the Symfony Standard Edition, the bootstrap file is automatically

rebuilt after updating the vendor libraries via the ``composer install`` command.

Bootstrap Files and Byte Code Caches

Even when using a byte code cache, performance will improve when using a bootstrap

file since there will be fewer files to monitor for changes. Of course, if this

feature is disabled in the byte code cache (e.g. ``apc.stat=0`` in APC), there

is no longer a reason to use a bootstrap file.

.. _`autoload.php`: https://github.com/symfony/symfony-standard/blob/master/app/autoload.php

.. _`bootstrap file`: https://github.com/sensiolabs/SensioDistributionBundle/blob/master/Composer/ScriptHandler.php