Problem with session

What version of CI did you have before upgrading? And what version did you install? It looks like you are using 3.x, not 4.0.2.

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And the problem seems to be that your MY_helper file is changing the session parameters while the session is already started.

You are rigth, I was mistaking, Im running 3.1.10. I use to have 2.2.6 
As for the helper the problem dosent seams to come from there because if I comment out the line nothing change.
What else could be?

If you made some change and still have errors, copy those new errors here. And put that in a “code” block. It’s easier to read.