Autoloader

<?php
function autoloader($classname) {
    $classname = str_replace("_", "\\", $classname);
    $classname = ltrim($classname, '\\');
    $filename = '';
    if ($lastNsPos = strripos($classname, '\\'))
    {
        $namespace = substr($classname, 0, $lastNsPos);
        $classname = substr($classname, $lastNsPos + 1);
        $filename = str_replace('\\', DIRECTORY_SEPARATOR, $namespace) . DIRECTORY_SEPARATOR;
    }
    $filename .= str_replace('_', DIRECTORY_SEPARATOR, $classname) . '.php';

    require $filename;
}

spl_autoload_register('autoloader');