Why is it "strongly recommended" not to use the env() helper when caching config files?

Question

Laravel upgrade documentation from 5.2 to 5.3 specifies the following:

Caching And Env

If you are using the config:cache command during deployment, you must make sure that you are only calling the env function from within your configuration files, and not from anywhere else in your application.

If you are calling env from within your application, it is strongly recommended you add proper configuration values to your configuration files and call env from that location instead, allowing you to convert your env calls to config calls.

The question the documentation doesn't answer is: why?

Shouldn't the env() helper, when used within the application, still work properly? Can't I still use env() after the config is cached, instead of being forced to finding it in my whole project and replacing it with the config() helper, as (indirectly) suggested by the docs?

For example, if I have this in my app.php:

'env' => env('APP_ENV', 'production')

and it will get cached with config:cache, but I still use the env() helper somewhere in the code, then is there any reason at all that env('APP_ENV') would give me something else than the config('app.env')?

And how about the App::environment() call - is using it also not recommended after config:cache is used on production?

Answer 1

This is because how caching works in Laravel, you have an storage/cache folder where is stored a "compiled" version of your configuration files when you use the command php artisan config:cache, so it is lighter and faster. In that caching process, Laravel reads the .env file and replaces all values using the env() helper function.

Now, to access the compiled version of the config, which is normally already in memory, you need to use the config() helper, otherwise you would be accessing a file, a much slower approach.

The reason behind disabling the env() function once you cached your configurations is to ensure the performance in the production enviroment, because it is assumed it is the situation where the compiling would take place.

In conclusion, it's the creator's decision, you may like it or not, IMO it makes things a bit cleaner and forces you to have a more optimized and organized application.

Hope this helps you.