How to learn CodeIgniter

kind of obvious but start with the tutorial in the codeigniter docs and do the tutorial more then once.  sign up for http://stackoverflow.com/questions/tagged/codeigniter and look at the codeigniter questions regularly. try to answer some  questions that you don't know the answer to - this will 'force' you to learn more about codeigniter, and you can read the other responses to see how else something can be accomplished.

google "robert martin" and "clean code". watch every video / lecture on youtube and vimeo, especially where he goes over refactoring and naming. his examples are going to be in java but it reads almost exactly like codeigniter.
https://www.youtube.com/results?search_q...clean+code

there a series of free codeigniter videos on net tuts. its old and they were created for codeigniter 1.7 -- but the basic concepts are all the same, and they  are great tutorials http://code.tutsplus.com/series/codeigni...-net-17602
warning that if you look up the author of those videos he now works with only laravel . oh well. there's also some paid courses on net tuts for codeigniter which are very good.

at the same time -- grind through basic php courses to keep increasing your php vocabulary.

my personal opinion that is very much in the minority (so don't flame me people because i already know you don't agree ) -- ignore any tutorial that insists you have to create a my_controller before doing anything else. start with the framework as it is without 'personalizing' it. ignore any tutorial that tries to be too clever like combining inserts and updates in one method.  there are a lot of books and tutorials that are just the author trying to show off. do not worry about DRY its overrated. do not worry about saving two lines of code. your focus should always be to make your code readable.  then as you refactor,  your code will become DRY while still being understandable.

Thanks @cartalot.. I will check out those videos too.. I have been watching Anthony Vipond's tutorials for sometime..