I recommend Kohana as a framework to work with (kohanaphp.com). It started as a branch of CI so is similar to that - but was totally rewritten with PHP5 support and lots of new stuff :)

Worth a look.

I always recommend Notepad++ plus a XAMPP installation over any form of IDE. It's simpler in the long run.

As to learning: that is a hugely personal thing. I picked it up over 4 or 5 years (still learning even now though!). If you already have a good grouding in general programming you wont have a problem :)

But with PHP learnign by doing is a good approach :) there are lots of snippet sites out there as well for you to peek through for ideas :D