Yii2 several sites, one core

Hi. I want to start work with yii2, trying configurate it to have opportunity store one core (yii2) in independent folder, update it etc and have independent app folders for several sites.

Thank you for a help)

I think I’ve read somewhere that this is not recommended. But would be the advantage to it this way? Why not having completely independend sites? Independency is always preferable.