[5.9] Add Env class

[kawax]

Again.
#28061

If other packages have global env(), the Laravel project will be broken. It actually happened.
The dependency package may have env() even if I do not install it myself.
This PR gives the option not to use env().

<?php

use Illuminate\Support\Env;

return [
    'name' => Env::get('APP_NAME', 'Laravel'),
];

It is necessary to consider whether to deprecate env().

Example of conflict

APP_DEBUG=false

Laravel env()
(bool)false

Another env()
(string)false
==(bool)true

Debug mode is enabled in production. Very dangerous.

[driesvints]

Please provide a thorough explanation in your original comment why this is needed and how it helps users and not just link to another issue/pr.

[kawax]

Currently, the frequency of encountering conflicts is low, so it is sufficient to be able to choose env() or Env.

[BrandonSurowiec]

Should there be a callback to customize the DotenvFactory parameters?

Env::setAdapters([
    new EnvConstAdapter,
    new PutenvAdapter,
    new ServerConstAdapter,
]);

Env::getAdapters(); // [new EnvConstAdapter, new PutenvAdapter, new ServerConstAdapter]

If a developer wants to customize the adapters in their AppServiceProvider it would allow them to do so.

The adapters are also referenced here:

https://github.com/laravel/framework/blob/5.8/src/Illuminate/Foundation/Bootstrap/LoadEnvironmentVariables.php#L92

It would be nice to centralize the adapters, but I'm unsure if customizing the callback in the AppServiceProvider would be early enough for the LoadEnvironmentVariables@createDotenv call.

[garygreen]

+1 from me. It's a nice way of cleaning up the code in helpers.php which often is a hive of random code and can be a cause of PR conflicts if lots of people touch it. I personally think helpers.php should just contain minimal code which hook into a class.

It also opens up possibilities of customising Env as @BrandonSurowiec mentioned, which could help potentially fix #27961 by giving devs an opporutnity to add PutenvAdapter if they need to support third party apps.