simple-psr4-autoloader.php

<?php
spl_autoload_register(function ($class) {
  //change this to your root namespace
	$prefix = 'vendor\\rootnamespace\\';
	//make sure this is the directory with your classes
	$base_dir = __DIR__ . '/classes/';
	$len = strlen($prefix);
	if (strncmp($prefix, $class, $len) !== 0) {
		return;
	}
	$relative_class = substr($class, $len);
	$file = $base_dir . str_replace('\\', '/', $relative_class) . '.php';
	if (file_exists($file)) {
		require $file;
	}

});