Autoloading

Composer loads the classes of CakePHP, of your application and of its plugins when they are first used. You don't include their files yourself, and you don't need App::uses().

Composer finds a class in one of two ways:

• A classmap is a list of the classes in some folders. Composer builds it when you run composer install, composer update or composer dump-autoload. Run composer dump-autoload after you add a class file to one of these folders.
• PSR-4 maps a namespace to a folder, for example App\ to src/. Composer finds a new class file without composer dump-autoload, unless you build an optimized autoloader with composer dump-autoload -o.

Run composer dump-autoload also after you change the autoload section of composer.json.

This page shows which of them each part of an application uses.

The Core

The classes of CakePHP are in the Cake namespace, in vendor/pieceofcake2/cakephp/src/. The composer.json of pieceofcake2/cakephp loads them with PSR-4 ("Cake\\": "src/").

The global names of CakePHP 2, such as Controller or CakeRequest, are aliases of the namespaced classes. When your code uses a global name first, an autoloader of the core loads the namespaced class. So both names work, and you need nothing in your own composer.json. See The Classes of the Framework.

An Application in the Modern Layout

The pieceofcake2/app skeleton loads src/ with a classmap:

"autoload": {
    "classmap": ["src/"]
}

The classmap finds the global classes in src/, such as AppController in src/Controller/AppController.php, whatever folder they are in.

For namespaced classes, add a PSR-4 entry, for example "App\\": "src/". Set App.namespace too, so that CakePHP finds your controllers, models and other classes by their short names:

"autoload": {
    "classmap": ["src/"],
    "psr-4": {
        "App\\": "src/"
    }
}

See Namespaced Classes.

An Application in the Legacy app/ Layout

List the folders of your classes in the classmap:

"autoload": {
    "classmap": ["app/Console/", "app/Controller/", "app/Lib/", "app/Model/", "app/View/"]
}

Then run composer dump-autoload and delete the App::uses() lines.

App::uses() is deprecated as of 2.13.0, but it still works. An application without a classmap keeps running. The first call in a process logs a warning, and with debug above 0 it also triggers E_USER_DEPRECATED. See Removing App::uses() calls.

Plugins

Composer loads the classes of a plugin when the composer.json of the plugin has autoload settings. When you write a plugin, add them as follows.

• In the modern layout, src/ holds the namespaced classes. Load them with PSR-4:

  "autoload": {
      "psr-4": {
          "ContactManager\\": "src/"
      }
  }

• In the legacy layout, the global classes are in Controller/, Model/, View/Helper/ and so on. Load them with a classmap:

  "autoload": {
      "classmap": ["Controller/", "Lib/", "Model/", "View/"]
  }

  List only the folders that the plugin has. composer dump-autoload stops with an error for a folder that does not exist.

A plugin that uses both layouts needs both entries.

For a plugin without these settings, add its folder to the classmap of your application, for example "classmap": ["src/", "plugins/MyPlugin/"].

See How To Create Plugins.

Vendor Files

Libraries installed with Composer are autoloaded and need no extra code.

Files that you copy into your project by hand go in vendors/ at the project root (app/Vendor/ in the legacy layout). Composer does not manage this folder, but it can load its classes. Add the folder to the classmap:

"autoload": {
    "classmap": ["src/", "vendors/"]
}

Load files that do not contain a class, or whose class differs from the file name, with App::import(). See Loading Vendor Files.

Overriding Core Classes

A copy of a core class in src/Cake/, at the path of its namespace, replaces the class of the core. Exclude the core file with exclude-from-classmap. See Overriding classes in CakePHP.