forward(REFERER) help

<?php
/**
 * Action for adding a wire post
 *
 */

// don"t filter since we strip and filter escapes some characters
$body = get_input("body", "", false);

$access_id = (int) get_input("access_id", ACCESS_PUBLIC);
$method = "site";
$parent_guid = (int) get_input("parent_guid");

// make sure the post isn't blank
if (empty($body)) {
    register_error(elgg_echo("thewire:blank"));
    forward(REFERER);
}

$guid = thewire_tools_save_post($body, elgg_get_logged_in_user_guid(), $access_id, $parent_guid, $method);
if (!$guid) {
    register_error(elgg_echo("thewire:error"));
    forward(REFERER);
}

// Send response to original poster if not already registered to receive notification
if ($parent_guid) {
    thewire_send_response_notification($guid, $parent_guid, $user);
    $parent = get_entity($parent_guid);
    forward("thewire/thread/$parent->wire_thread");
}

system_message(elgg_echo("thewire:posted"));
forward(REFERER);      

i am creating new plugin...when users was posted in thewire forward into activity page

change into forward('activity')....but not working for me...