session_write_close(): Failed to write session data using user defined save handler

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PHP.net - session_write_close

It seems that the output buffering is causing session problems on php 7+

Well, I set output buffering = off in php.ini but it doesn't solve the problem. I still get "Failed to write session data using user defined save handler" randomly.

I find this thread on stackoverflow : https://stackoverflow.com/questions/3411...ssion-data
Not sure if the selected answer can apply to codeigniter ? I'm using Redis.