elgg_echo($message_key, $args=array(), $language="")
Given a message key, returns an appropriately translated full-text string.
elgg_error_response($error= '', $forward_url=REFERRER, $status_code=ELGG_HTTP_OK)
Prepare an error response to be returned by a page or an action handler.
elgg_ok_response($content= '', $message= '', $forward_url=null, $status_code=ELGG_HTTP_OK)
Prepares a successful response to be returned by a page or an action handler.