For most of us, CodeIgniter is a great PHP framework. From my point of view, it is the best PHP framework and I am not impressed about the great evolution it have been reaching during past year, because after using lots of PHP frameworks (CakePHP, Symfony, etc.) I finally focused on CodeIgniter framework for my PHP projects.
It has an active online community, great performance, it is customizable enough, it has an excellent and neat documentation, Object Oriented features and there is a great team behind the scene.
Moreover, you can easily use CodeIgniter applications in major shared hosting services. Then, if your application has success you can of course migrate you a powerful server without any major problem. Installation is very easy and the file structure is customizable for our own needs. I had a project where I needed to use CodeIgniter in Windows, for my surprise it worked very well on SQL Server and IIS thought fast-cgi.
The learning curve is extremelly fast and with CodeIgniter you can easily build any kind of web application including multi-language applications, membership applications, database driven applications, and so on.
The best practices in software development has been embeeded in this framework.
