Role Base Access Control System

I have to refactor old application made in PHP combined with codeigniter version 3.0.6. what is the best solution to implement role base access control system to assign some rules ?  I am new in codeigniter and I will be very thankfull for all suggestions. 

Community Auth

What did you Try? What did you Get? What did you Expect?

Joined CodeIgniter Community 2009.  ( Skype: insitfx )