Namespace-private class properties

(NB: This idea is NOT about namespace visibility for classes, interfaces or traits (already discussed here: https://wiki.php.net/rfc/namespace-visibility). It's about adding a *new* visibility qualifier, call it "internal", to make properties private inside a namespace. The purpose is to make composition less fragile by not exposing more than necessary.) (NB: This feature exists in Swift, described here: https://docs.swift.org/swift-book/LanguageGuide/AccessControl.html) We have public, protected and private. Since PHP has no module system, we have no qualifier to mark a class property as "private for this module". One solution to this could be to add a new qualifier "internal", to make properties public within the current namespace. Use-cases: * Split data and behaviour into different files and classes * Safely skip getters and setters without risk of properties being abused by client code Tiny example: ``` namespace App\User; class User { internal $username; internal $password; } namespace App\User\Services; class ProcessUser { // Child namespace has access to internal properties, // but App\ has not. } ``` Possible? Olle