login system with CI 3.0

Welcome to CodeIgniter.

All the major changes between CI2 and CI3 can be found in this post http://forum.codeigniter.com/thread-1657...ml#pid7480

Another small note. When it comes to user management and login functionality, I highly recommend using a proven and secure auth library. Developing an authentication feature involves a lot of security that is easy to miss and the smallest mistake can open up big security holes. Personally I would recommend Ion Auth

Whit that said, building an auth feature your self will teach you a lot, and you will learn from it if you never done it before. So I encourage you to do it! Test and play around to learn, and ask questions if you get stuck.
But I again recommend using a proven auth library for anything used in production, it's just to easy to make mistakes with something that need that high level of security.