I’m running into a major problem when I try to update an install of EE 2.1.0 to something later (I have tried 2.2.1, 2.2.2, and 2.3.1).
When I replace all the appropriate files (I know which ones to replace; I update EE instances a lot…) and then head over to /system/index.php - I get the following error:
Fatal error: Call to undefined method CI_Config::CI_Config() in /Volumes/Data/Sites/**/system/expressionengine/core/EE_Config.php on line 42
I’m completely lost as to what to do.