The original idea of this PR was to allow injecting string $env into php config closures. Even though this can be done by injecting ContainerConfigurator & calling env() it seems kind of redundant when you don't need any features except the current env, eg when using the config builder classes:

- return function (AcmeConfig $config, ContainerConfigurator $c) {
+ return function (AcmeConfig $config, string $env) {
- if ('dev' === $c->env()) {
+ if ('dev' === $env) {
    // ...
  }
};

Injecting the $env variable looks a bit cleaner IMO.

However, while working on this PR I discovered #41182 . Even though there's already an $env variable presets in the scope of php files which can be used for the same thing, it's not really IDE friendly:

Since the original PR mentioned the that the $env variable was added for PHP <8 & Symfony 6.2 is >=8.1, it doesn't seem to be needed any more, so it can be deprecated.