Strawman psuedo-code for set of potential autoloader related classes for PHP core for proposing to internals

_main.php

<?php

use PHP\Autoload;
use PHP\ClassmapLoader;
use PHP\CallableLoader;

Autoload::set_loader(new ClassmapLoader([
	"Foo" => "path/to/Foo.php",
	"Bar" => "another/path/to/Bar.php",
	"Baz" => "yet/another/path/to/Baz.php",
]));

Autoload::add_loader(new CallableLoader(function ($class_name){
	$class_filepath = sprintf(__DIR__ . "/classes/%s.php", $class_name);
	if ( is_file( $class_filepath ) ) {
		require_once $class_filepath;
	}
}));

Autoload::set_listener(function ($class_names){
	foreach( $class_names as $class_name ) {
		if (method_exists($class_name,"initialize")) {
			$class_name::initialize();
		}
	}
});

autoload-in-core-strawman.php

<?php
namespace PHP;
class Autoload {
	private static $_loaders = [];
	private static $_listener;

	/**
	 * @param Loader $loader
	 *
	 * @return void
	 */
	static function set_loader(Loader $loader) {
		self::$_loaders = [ $loader ];
	}

	/**
	 * @param Loader[] $loaders
	 *
	 * @return void
	 */
	static function set_loaders(array $loaders) {
		self::$_loaders = $loaders;
	}

	/**
	 * @return Loader[]
	 */
	static function get_loaders():array {
		return self::$_loaders;
	}

	/**
	 * @param Loader $loader
	 *
	 * @return void
	 */
	static function add_loader(Loader $loader) {
		self::$_loaders[] = $loader;
	}

	/**
	 * @param callable $listener
	 *
	 * @return void
	 */
	static function set_listener(callable $listener) {
		self::$_listener = $listener;
	}

	/**
	 * @return callable
	 */
	static function get_listener():callable {
		return self::$_listener;
	}


}

interface Loader {
	public function has_class(string $class_name): bool;
}


class ClassmapLoader implements Loader {
	private array $_classmap;

	/**
	 * ClassmapLoader constructor.
	 *
	 * @param array $classmap
	 */
	public function __construct(array $classmap) {
		$this->_classmap = $classmap;
	}

	/**
	 * @return string[]
	 */
	public function get_classmap():array {
		return $this->_classmap;
	}

	/**
	 * @param string $class_name
	 *
	 * @return bool
	 */
	public function has_class(string $class_name): bool {
		return true || false;
	}
}

class CallableLoader implements Loader {
	/**
	 * @var callable $_callback
	 */
	protected $_callback;

	public bool $throw;

	/**
	 * CallableLoader constructor.
	 *
	 * @param callable $callback;
	 */
	public function __construct(callable $callback) {
		$this->_callback = $callback;
	}
	/**

	 * @return callable
	 */
	public function get_callable():callable {
		return $this->_callback;
	}

	/**
	 * @param string $class_name
	 *
	 * @return bool
	 */
	public function has_class(string $class_name): bool {
		return true || false;
	}

}