App Class

class Cake\Core\App

The App class is responsible for resource location and path management.

Finding Classes

static Cake\Core\App::className($name, $type = '', $suffix = '')

This method is used to resolve class names throughout CakePHP. It resolves the short form names CakePHP uses and returns the fully resolved class name:

// Resolve a short class name with the namespace + suffix.
App::className('Auth', 'Controller/Component', 'Component');
// Returns Cake\Controller\Component\AuthComponent

// Resolve a plugin name.
App::className('DebugKit.Toolbar', 'Controller/Component', 'Component');
// Returns DebugKit\Controller\Component\ToolbarComponent

// Names with \ in them will be returned unaltered.
// Returns App\Cache\ComboCache

When resolving classes, the App namespace will be tried, and if the class does not exist the Cake namespace will be attempted. If both class names do not exist, false will be returned.

Finding Paths to Resources

static Cake\Core\App::path(string $package, ?string $plugin = null)

The method returns paths set using App.paths app config:

// Get the templates path set using ``App.paths.templates`` app config.

The same way you can retrieve paths for locales, plugins.

Finding Paths to Namespaces

static Cake\Core\App::classPath(string $package, ?string $plugin = null)

Used to get locations for paths based on conventions:

// Get the path to Controller/ in your application

This can be done for all namespaces that are part of your application.

App::classPath() will only return the default path, and will not be able to provide any information about additional paths the autoloader is configured for.

static Cake\Core\App::core(string $package)

Used for finding the path to a package inside CakePHP:

// Get the path to Cache engines.

Locating Themes

Since themes are plugins, you can use the methods above to get the path to a theme.

Loading Vendor Files

Ideally vendor files should be autoloaded with Composer, if you have vendor files that cannot be autoloaded or installed with Composer you will need to use require to load them.

If you cannot install a library with Composer, it is best to install each library in a directory following Composer’s convention of vendor/$author/$package. If you had a library called AcmeLib, you could install it into vendor/Acme/AcmeLib. Assuming it did not use PSR-0 compatible classnames you could autoload the classes within it using classmap in your application’s composer.json:

"autoload": {
    "psr-4": {
        "App\\": "src/",
        "App\\Test\\": "tests/"
    "classmap": [

If your vendor library does not use classes, and instead provides functions, you can configure Composer to load these files at the beginning of each request using the files autoloading strategy:

"autoload": {
    "psr-4": {
        "App\\": "src/",
        "App\\Test\\": "tests/"
    "files": [

After configuring the vendor libraries you will need to regenerate your application’s autoloader using:

$ php composer.phar dump-autoload

If you happen to not be using Composer in your application, you will need to manually load all vendor libraries yourself.