Cannot pass variables from Controller to Model

The code I put here is just a test.. not my site source code. (Clean install CI 3.06 and CI 2 to simply test it )
Just let you know it works in CI 2 (works in any controller), but CI 3 doesn't (only works in MY_Controller).

The strange thing is, it works only set variables in MY_Controller.

If it is bad coding habit, CI 3 should deprecate it, not allow only set variables in MY_Controller, it makes confusion.

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