yii2-coding-standards | Yii 2 coding standards | Web Framework library

First of all the extension, you are trying to install you should know the purpose why it should be used and when.

From The Yii 2 Core Framework Code Style

The following code style is used for Yii 2.x core and official extensions development. If you want to pull-request code into the core, consider using it.

We aren't forcing you to use this code style for your application. Feel free to choose what suits you better.

It is only used when you are developing Yii2 not working WITH Yii2 means only if you are going to contribute to the core functionality of the framework then use this extension

If you are working on a project which is using Yii2 framework, you don't need to install this extension as the PHPCS can directly work in this case if you have it installed, all the standards that are used already are in PHPCS are not much different,

You dont need this extension, leave it, PHPCS can do the work directly.