How to change the app environment at run time?

PHP Snippet 1:

dump(config('app.env')); // "testing"

config(['app.env' => 'production']);

dump(config('app.env')); // "production"

PHP Snippet 2:

dump(app()->environment()); // "testing"

app()['env'] = 'production';

dump(app()->environment()); // "production"

PHP Snippet 3:

$this->app['env'] = 'production';