Theme hook problem

=========================================================plugins/urlrules/urlrules.plugin.php - Code=========================================================<?php/** * A plugin for Habari that displays archives page under top menubar * which is based on the URL Rules plugin from Drunken Monkey Labs * * Usage: * <code>echo $archivesmenu;</code> * */class URLRules extends Plugin{	function info()	{		return array (			'name' => 'URL Rules',			'version' => '1.0',			'author' => 'Chris Starjive',			'license' => 'Apache License 2.0',		);	}	public function action_add_template_vars( $theme )	{	  $theme->archivesmenu= "<li><a href='<?php Site::out_url( 'habari' ); ?>/archives' title='Archives'>Archives</a></li>";	}	public function load()	{		CRewriter::add_rule( 'display_archives', '%^archives(?:/(?P<year>\\d+))?/?$/?$%i', 'archives(/{$year})', 'UserThemeHandler', 'display_archives', 1 );	}	}=========================================================themes/k2/header.php - Code=========================================================<?php echo $archivesmenu ?>=========================================================Problem that i got showing in my header is this.=========================================================Notice: Undefined variable: archivesmenu#0 in user\themes\k2\home.php:1: include('D:\\Server\\www\\user\\themes\\k2\\header.php')#1 in system\classes\rawphpengine.php:90: include('D:\\Server\\www\\user\\themes\\k2\\home.php')#2 in system\classes\theme.php:376: RawPHPEngine->display('home')#3 in system\classes\theme.php:115: Theme->display('home')#4 in system\classes\theme.php:218: Theme->display_fallback(array ( 0 => 'home', 1 => 'multiple', ))#5 in system\classes\theme.php:239: Theme->act_display(array ( 'fallback' =>  array (   0 => 'home',   1 => 'multiple', ), 'user_filters' =>  array (   'content_type' => '1', ), ))#6 in system\classes\userthemehandler.php:39: Theme->act_display_home()#7 in system\classes\controller.php:155: UserThemeHandler->act('display_home')#8 in index.php:146: Controller::dispatch_request()