We are considering using Yii for a refactoring of a commercial web application that we distribute to clients.
We are considering Yii vs Zend Framework 2. Overall we like Yii better except for the fact the Zend Framework has Zend (a larger company) backing it so we know its development will be strong many years from now.
Does anyone have any thoughts on this? We’ve seen many frameworks come and go so this is our only concern. Any words of encouragement? 
Yii is past the 1.1 mark, so it is by definition stable and ready for production use.
And you can use Zend with Yii.
The MVC of Zend really is lacking a lot of elegance in my opinion…
It is the underlying technology which matters, and they are both based on PHP.
In the end you should choose the framework which makes you happy and more productive.
Yii is not a mayfly (here today, gone tomorrow).
It’s here to stay.
Worst case scenario you’ve got a well written guide and api and you can probably figure it out