I came across this little benchmark/comparison of some frameworks - it includes Yii:
http://phalconphp.com/documentation/benchmark
Yii scores amazingly well in all of those benchmarks!
Except for the last one: memory usage of the framework, where Yii scores worse than any other framework. I wonder why the memory use is so high compared to other frameworks? 3.5 MB compared to e.g. Fuel at 1 MB, is a pretty substantial difference. Is any consideration being given to lowering the memory-footprint of Yii 2.0?
Note that one aspect of this benchmark you can safely ignore, is "framework time per request" - Yii is as fast as the fastest PHP frameworks, and yes, Phalcon is faster, but instead of being taken and impressed by the blue bars, pay attention to the actual numbers: Yii at 1.311 and Phalcon at 0.385.
In my opinion, all this proves, is that maintaining a C codebase is not worth the effort - with less than one millisecond saved per request, there is only a very few, very marginal applications where this would actually matter. Basically, in any application that uses a relational database, one millisecond won’t matter at all, because the bottleneck is the database, and the 1 millisecond of overhead per request is insignificant compared to even a single database PK query and roundtrip.
I can’t see how this type of optimization delivers any significant value, but what it does deliver, is a codebase that is far less accessible to those trying to understand the inner workings of the framework, setting a high barrier for potential framework-contributors, effectively putting a cap on contributions.
For 99% of applications, this optimization won’t matter at all. If I did have to write an application where request overhead was this critical, I would not write that component of the application in PHP in the first-place. I hope Yii does not take that course.