I use ZF a lot and I like it very much. I've learned how to solve a big part of perfomance problems with ZF, so it's became not "enormous" and "monstrous" for me.
But I'd like to know if there are any as powerful frameworks as Zend for PHP. Maybe CodeIgniter is? What is it? What are its cool features? Anything else?
And, are there any powerful frameworks which realises not MVC? Powerful means not just implementing of design pattern but a library of useful classes, functions, etc
There is a difference between frameworks, some are regualr frameworks (used to be called 'class libraries'), and some are 'full stack frameworks' (used to be called 'frameworks'). The web is and will always be about buzz-words...
Zend is a regular framework, which means you can use it's components separatly, and you aren't forced to use them. In a full stack framework, like CakePHP (I don't reallt know code igniter), you are locked inside. You can only use it's classes and they are hard to extend.
If you are looking for a competitor for ZF, be sure not to compare it with a 'full stack' framework, because it's a different thing, and it solves different problems...
Other then that, I don't know any frameworks that do not implement or give you the possibility to implement MVC, just because it's very applicable to web applications.
I'm a big ZF fan, but you can take a look to Symfony which is pretty powerfull but maybe a little to heavy sometimes.
I'd personally recommend Kohana. They just released 3.0 less than a week ago (it's in the forums, not on the dl page). It used to be a branch of CodeIgniter for PHP5, but it just underwent a big rewrite so now it's much cleaner and faster.
Basically, it does just enough to help you, but stays the hell out of your way. It's very lightweight and fast. It beats the pants off of pretty much any other framework I've used - Zend, Symfony, CakePHP, and CodeIgniter.
The thing about Zend is that you can actually decouple its components. You can use them without using the rest of the framework (just register the autoloader). Really, Zend to me is more like a heavy framework with a bunch of PEAR libraries in it. The framework is too heavy for normal use, but the components are nice.
I personally like CodeIgniter, it is good to start from 0 due to its great documentation and it can be easily expanded with the lot of plugins. It is considered pretty fast framwework (faster than ZF, Cake php and Symphony) however its speed is lowered by PHP4 support and any framework will lose its speed as you add new libraries and plugins there.
ZendFramework is the most powerfull php framework I have found. CodeIgniter is a lightweight MVC framework so its not powerful. ZendFramework also has loose coupling so you can use some Classes without other classes like the front controller.
CodeIgniter MVC is not as powerful and the ZendFramework MVC but i haven't tried any other framework
I've choosen CodeIgniter because it is lightwight and because i'm not using a ORM and Smarty, this means i only need the router and controller/model class.
But it is missing a few features like user/login handling being the most serious. I also use some zend classes like amazon access.