Autoloading Class files and instantiating a class - Admin backend At the moment I am auto loading my classes with:

spl_autoload_register(function ($class) {
    require_once 'classes/class.'. $class .'.php';
});


And instantiating the class with:

$backend = new backend();
$dashboard = new dashboard();
$article = new article();
$video = new video();
$theme = new theme();


These are in a config file required on every action page of my admin section.

backend is my main class holding database functions and other global functions.

The other classes all extends backend.

As I understand it, I could call backend functions through for example article, as it is an extension of the class.

Is this a good method for instantiating the classes, or is there a way I can call them automatically without having to write these in the config file at all?
Using spl_autoload_register() is a well known and recommended way of auto-loading classes. 

And of course you can't call objects without having them instantiated first.