Plugins
CakePHP allows you to set up a combination of controllers, models, and views and release them as a packaged application plugin that others can use in their CakePHP applications. Have a sweet user management module, simple blog, or web services module in one of your applications? Package it as a CakePHP plugin so you can pop it into other applications.
The main tie between a plugin and the application it has been installed into, is the application's configuration (database connection, etc.). Otherwise, it operates in its own little space, behaving much like it would if it were an application on its own.
Many plugins written for CakePHP 2 were never updated for PHP 8. The Piece of Cake 2 project maintains PHP 8 compatible forks of popular plugins such as DebugKit, Bake, Upload and TwigView; see Repositories and Plugins for the full list. Other plugins that require cakephp/cakephp 2.x can still be installed, because pieceofcake2/cakephp replaces that package in Composer, but you need to check yourself whether they work on PHP 8.