In my current project I have a login form I want to validate with Ajax. If everything is ok, the user should be redirected to the respective start page. As it seems to be impossible to do the redirect on the server-side (at least to me), I do it on the client-side. I use the following snippet in my view:

<div id="login">
    <?php echo $ajax->form(array('action' => '/login'), 'post',
                                              array('update' => 'login')); ?>
    ...
    </form>
    <?php if (isset($url)) echo $javascript->codeBlock('window.location = "'.$url.'"'); ?>
</div>

And in my controller I use the following code:

if ($this->RequestHandler->isAjax())
{
    $this->set('url', '/'.$page);
}
else
{
    $this->redirect($page);
}