Change record status: 
Introduced in branch: 


Drupal 8 now ships with a PSR-4 autoloader with support for PSR-0 disabled.

See also:

Drupal core now ships with Composer. This means all core- or module-provided classes that follow the PSR-4 standard (excluding the disabled PSR-0 support) will be autoloaded by the system, provided they are placed in the correct directory.

Drupal core uses the following namespaces and directories:

Namespace Directory
Drupal\Core core/lib/Drupal/Core/
Drupal\Component core/lib/Drupal/Component/

Modules should place their classes in a modules/$module/src

Namespace Directory
Drupal\comment modules/comment/src/
Drupal\entity modules/entity/src/
Drupal\node modules/node/src/
Drupal\taxonomy modules/taxonomy/src/

The registry system that is built on top of files[] declarations has been removed, as has hook_registry_files_alter(). All classes provided by module must be converted to PSR-4 and files[] = entries can then be removed in the file.

See Core subsystems converted to PSR-4 standard for more information.

Module developers
Updates Done (doc team, etc.)
Online documentation: 
Not done
Theming guide: 
Not done
Module developer documentation: 
Not done
Examples project: 
Not done
Coder Review: 
Not done
Coder Upgrade: 
Not done
Other updates done
As of this writing we still need to document that core now uses PSR-0.


donquixote’s picture

Besides, modules should namespace their classes as
"Drupal\$module_name\..", with optional sub-namespaces.

Module-provided classes that are namespaced this way will be easily found by the autoloader.
For module-provided classes in foreign namespaces, we need a registration or discovery mechanism that has not yet been decided on. (but it will not be the files[] from D7)

mossy2100’s picture

I have a bunch of classes written for Drupal 7 that I have decided to convert to PSR-0, partly for the exercise and partly for future migration to D8. Do I have to create a module and put these classes (with PSR-0 namespace subdirectories) in in sites/all/modules/my_module/lib? Or should I/can I place the classes in sites/all/vendor or sites/all/libraries? I realise for my D7 site it doesn't really matter, so my question is, what will be the requirement for D8?

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socketwench’s picture

The PSR-0 classloader converts underscores in class names into directory separators. As a result:

namespace Drupal\myModule\stuff;

class My_Stuff {

Saved in file drupalRoot/modules/myModule/lib/myModule/stuff/My_Stuff.php will never load.

The autoloader will instead attempt to find the class at:


Removing the underscore from the file and class name (MyStuff) avoids the issue.

donquixote’s picture