Idea: Allow PHP class declaration across multiple files

example.php

// In /index.php
spl_autoload_register(fn($c) => require sprintf( "%s/src/%s.php", __DIR__, $c ));

// In /src/FooBarCms.php
class FooBarCms {}

// In /plugins/my-map/src/MyMap.php
class MyMap {
  function display() {}
}

// In /plugins/my-map/extends/FooBarCms.php
extends class FooBarCms {
  public $map;
  function __construct() {
    $this->map = new MyMap;
  }
}

// In /plugins/my-map/index.php
spl_autoload_register(fn($c) => require sprintf( "%s/src/%s.php", __DIR__, $c ));
register_class_extends(FooBarCMS::class,__DIR__ . '/extends' );
$cms = new FooBarCms();
$cms->map->display();