How much PHP should one know BEFORE using CodeIgniter?

[eluser]Dam1an[/eluser]
Derek (on of the team behid CI) made a post (here) about learning PHP and CI (Codeigniter) at the same time.

Personally, I think as long as you have a reasonable understanding, and can follow the basic logic of some existing PHP code, then you know enough to get started
I would recommend you look into OOP (Object Orientated Programming) assuming you will be using PHP5 as its better (IMO) then procedural PHP

2 Very important sites white learning are the PHP docs and the user guide, make sure you bookmark both (I lied, Googles your thrid resource )

Any other questions and I'm sure someone will be more then happy to help