How / When / How 'env' is parsed?

Dear community,

I was a CodeIgniter 3 user, and now diving into CodeIgniter 4.

I am trying to use 'env' functionality, but even if I un-comment the
line for CI_ENVIRONMENT, the variable ENVIRONMENT value still 'production' in my code.

I have tried

PHP Code:

getenv('CI_ENVIRONMENT') 


but it is not defined.

To follow, I have added a variable as the documentation said, MYTEST = "value1" in the 'env' file,
and in a controller, using

PHP Code:

getenv('MYTEST') 


returns undefined.

I am probably doing something wrong, thank you for your lights!

glihm