Cannot pass variables from Controller to Model

Is it a bug in CodeIgniter 3 ?

It is very strange. If I set a variable in MY_Controller, any model can receive this value.

But if I set a variable in normal Controller, any model can not. receive this value.

I believe it is a bug because CodeIgniter 2.x works good, but CodeIgniter 3 doesn't.



Test



I set a variable in MY_Controller 

Code:

$this->test_message = 'this is a test';

Echo this variable in Model

Code:

echo 'ttt: ' . $this->test_message;

It works.


But if I set it in  normal Controller


Error



I found this issue from upgrade my old website from Codeigniter 2 to 3.


How to solve this issue?

Personal blog: https://terryl.in
My personal project is called Dictpedia is currently using Codeigniter 3, welcome.