RedirectController.php

<?php

class RedirectController extends Controller
{

    private static $allowed_actions = [
    ];

    public function init()
    {
        parent::init();

        $host = $this->request->getHeader('Host');
        $path = $_SERVER['REQUEST_URI'];
        $redirects = Redirect::get_by_url($host, $path)->sort('Priority DESC, ID ASC');

        if ($redirects->count()) {
            foreach ($redirects as $redirect) {
                /** @var Redirect $redirect */
                if ($redirect->matchesParams($_GET)) {
                    $redirectLink = $redirect->replaceRequest($host . $path);
                    // SS can not handle 308 Permanent Redirect. See SS_HTTPResponse
                    if ($redirect->ResponseCode == 308) {
                        header('Location: ' . $redirectLink, null, 308);
                        exit;
                    } else {
                        return $this->redirect($redirectLink, $redirect->ResponseCode);
                    }
                }
            }
        }

        return $this->httpError(404, "Nowhere to go.");
    }
}