What is the best PHP framework?

1- Yii
2- Code Igniter- Zend Framework
3- CakePHP In fact I would have to say that Zend Framework and Code Igniter share an equal second for me as they’re just so different that it’s not really possible to say one is better than the other and should be chose over the other.
Zend Framework & Code Igniter : requires a lot of work, the documentation is overwhelming while still not being that great, and it just doesn’t feel right to me.
CakePHP : it really forces into doing things the way it wants you to do things and the moment you want to get into something a little more out of the ordinary (which often I do to improve performance) it can’t handle it and it’s also quite slow.
Yii :I guess the thing with Yii is that it fits in nicely right between Zend Framework and Code Igniter.
It’s probably not the simplest to learn for a PHP or OO novice, but for an experienced OO developer it’s a breeze.
It has great documentation and if need be you can always inspect the code yourself.
I actually spend quite some time developing in ASP.NET and Yii feels very very similar.
SO "Yes It Is!"

This is a big question that a lot of developers are asking about these days.
But it's difficult to answer because framework is a tool designed to solve problems and as we know every framework have a lot of features that not supported in another one, so your question will be - which framework fit your project (website) ? - and then pick it, it will be the best framework for you.
And for knowledge sharing reason, i used "Symfony Framework" it's a good one for a big and huge websites.

For small projects (or if you'r only one programmer), small, fast and easy solution: Slim PHP Framework + Paris & Idiorm (database access) + Twig (template engine)

The question is totally wrong , we can't ask what's the best php framework you may , ask what's the best framework to use for developing an application that support (blablab) and use(blabla) . but I may also add another framework that I use myself for some projects , Laravel4 is the one that I use in my side.

It is not evident to judge what is the best framework.
It depends on the project specifications and requirements, users number, ...

If you are looking for php framework then I will recommend "CodeIgniter".
It is very easy to learn and use.
It is fast than other frameworks like Zend and CakePHP.
You can start working in it very quickly.
You can start building its modules with in 1 - 2 hours if you know MVC structure.
Just download and install PYROCMS.
It is codeigniter based.
Download a Sample module of PYROCMS and study it.
I am sure you will comfortable with its development with in 1 - 2hours if you are good learner.

I recommend Yii as well ..
but that is based on my personal experience, I did a lot of research just to select the framework that "SUITS ME BEST" and Yii was the result ..
but again I want to emphasize on the fact that there are different factors in which we could say this framework is better than the others but the most important factor is "WHICH ONE YOU & YOUR TEAM FEEL COMFORTABLE WORKING ON".

As a lot of people said, choose a framework that will suit your needs.
Look at what is required for your project and what your personal requirements are.
Personally I don't believe that one framework is necessarily better than another or even easier to learn than another, but it really depends on your experience as a developer and your project needs.
Also, when the documentation becomes a problem, you will find a lot of extra information through forums for that framework, so for example, even though the docs on the Zend pages might not be sufficient, there's stacks of information and videos all over the web that should suffice.
The same applies for all the other frameworks.

I strongly recommend Yii.
Very comprehensive, easy to pick up, plenty of extensions and great performance.

I have been using Yii framework for almost three years and it is great framework , have a good structure of mvc and better than others .

the Best framework is Laraval, for begenner i suggest codeigniter.