Very simple PSR-4 autoloader

psr4.php

<?php

namespace your\namespace\here;

spl_autoload_register(function($class) {
		if (stripos($class, __NAMESPACE__) === 0)
		{
			@include(__DIR__ . DIRECTORY_SEPARATOR . 'classes' . str_replace('\\', DIRECTORY_SEPARATOR, strtolower(substr($class, strlen(__NAMESPACE__)))) . '.php');
		}
	}
);

// Just put this file in the root directory of your project and include it in your bootstrap file and update the namespace.
// File name should be lowercase.
// File name should have .php extension, if you want using an another extension, update line 8 accordingly.
// Search class in "classes" directory, if you want using an another directory, update line 8 accordingly.