Autoload classes with spl_autoload_register

// PSR-0: namespace separators and underscores both become directories
spl_autoload_register(function ($class) {
    $name = str_replace(array('\', '_'), DIRECTORY_SEPARATOR, ltrim($class, '\'));
    $path = __DIR__ . '/lib/' . $name . '.php';

    if (is_readable($path)) {
        require $path;
    }
});