14.1. When to Create a New Module?

A module is an autonomous and reusable unit of your application. By default your application has the single Application module. And it is normal to put your models, views and controllers in this module, especially in a simple website.

A module can contain models, views, controllers and assets. Module classes typically live in a separate namespace (the same as module name). Module has its own configuration file where you can register routes, controllers, controller plugins, services, view helpers and so on.

You may need to create a new module when any of the following is true:

• If your website is relatively large and dividing it into pieces would make it easier to maintain. For example, you can introduce the Admin module and put your backend functionality into that module.
• If the functionality you are implementing is autonomous (has no or few dependencies on other modules of your application. For example, the Blog functionality in theory can be separated in another module, because it does not depend on the rest of the application, but the application depends on it.
• If a module can be separated from your application and concurrently used in another project. For example the Blog module can be reused in another project without changes (only its configuration may require changes).

In any case, real life is complex, and you should be guided by the intuition when it seems that it is necessary to create a new module. If you think that separating a functionality into a module gives you some significant benefits, create the module.

At the same time, you should not create a huge number of almost empty modules, it is better to combine related functionality in a single module.