How to use spl_autoload_register for multiple diectories in PHP?

I'm actually trying to create a MVC framework for my own, however I'm having troubles with the Autoload. It's not a problem actually, but I'd like to ask the gurus, how are they using the spl_autoload_register function when there are different directories.

Lets say we have the following directories:

Controllers
Libs
Models

Each folder contains different classes, like:

Controllers:
   Main.php
   File.php
   About.php
Libs:
   Main.php
   Front_controller.php
Models:
   Index.php
   File.php
   Login.php

You can notice that some file names might be found with the same name in different directories. Okay, so this is what I've tried so far:

spl_autoload_register(function ($class) { 

    $pathContorllers = 'Controllers/' . $class . '.php';
    $pathLibs = 'Libs/' . $class . '.php';
    $pathModels = 'Models/' . $class . '.php';

    if (file_exists($pathContorllers)) {
        require_once $pathContorllers;
    } elseif (file_exists($pathLibs)) {
        require_once $pathLibs;
    } elseif (file_exists($pathModels )) {
        require_once $pathModels ;
    }
});

It is working well, however I'm sure that there is another way to make everything simpler. Can anyone suggest me how can I make this code better or simpler / what are gurus using in this situation?