What should my controller return in a Craft.postActionRequest
If you're just looking to return true or an error message from your controller's action, then it should probably be something like:

$this-&gt;returnJson(array('success' =&gt; true));


Or on error:

$this-&gt;returnErrorJson($e-&gt;getMessage());


returnErrorJson will set an 'error' key and pass whatever mess you use as its value.