<?php

spl_autoload_register(
    function($className) {
        $fileParts = explode('\\', ltrim($className, '\\'));

        if (false !== strpos(end($fileParts), '_'))
            array_splice($fileParts, -1, 1, explode('_', current($fileParts)));

        $file = implode(DIRECTORY_SEPARATOR, $fileParts) . '.php';

        foreach (explode(PATH_SEPARATOR, get_include_path()) as $path) {
            if (file_exists($path = $path . DIRECTORY_SEPARATOR . $file))
                return require $path;
        }
    }
);