Yii2 port of the famous NestedSetBehaviour: nestedsetbehavior
You can find the repo here: GitHub Respository
You can also find the packagist here: Packagist Repository
Please refer to the original documentation on how to use this, I have literally just replaced the functions contents for Yii2.
This class is, just like Yii2, still unstable, use at your own risk. I have done a fair bit of testing but you will find bugs.
You can open an issue on GitHub when you do: GitHub Issues