Any plans to migrate to yii2

No plans for now, i don't think a migration can even be done given the amount of custom classes we have in place, rather a rewrite in Yii 2 but that would be too time consuming and at this point i don't really see any benefit.

If i were to go with Yii2, i would also correct all the app design mistakes i did in the current mailwizz, and it won't be compatible with the current mailwizz app, so we will have a Mailwizz 2.0 :D

On another note, they just released 1.1.18 and i upgraded the framework to that version, which fixes some php 7.1 issues, so now we should support php 7.1 just fine.
Many thanks @twisted1919

We are planning to build ab application that is tightly integrated with mz and we need to know yii1.1 or yii2

It seems we have to go with yii1.1