Can't switch to production mode

Hi all, 
I can't switch to production mode. I still have the CI_ENVIRONMENT variable set to development. 
I use the.env file. 
I changed the CI_ENVIRONMENT production line in the .env file (uncommented). 
I checked my .htaccess file in the public folder (just to be sure, no SetEnv here). 
It's very strange. With the CI_ENVIRONMENT production in the .env file, if I check $_ENV array, I can see CI_ENVIRONMENT still set to development.
But, if I check $_SERVER array, I can see CI_ENVIRONMENT set to production. 
If change again in development and check again the two arrays, I see $_ENV still in development and $_SERVER has been updated in development. 
Seems that the framework update only the $_SERVER array from my .env file change.
Other variables, like an API token, are updated in both arrays and I can see the variable updated using env() function.
I ran out of ideas. Any help to understand this?

Solved!
I need to restart php spark serve

Any time you make any changes you do need to re-start the server.

What did you Try? What did you Get? What did you Expect?

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