static function getFriendGuidCSString($owner)
 {
     $friends = self::getFriends($owner);
     $friend_guids = array();
     if ($friends) {
         foreach ($friends as $friend) {
             $friend_guids[] = $friend->guid;
         }
     }
     return arrayToCSSString($friend_guids);
 }
<?php

/* * ***********************************************************************
 * 
 * SocialApparatus CONFIDENTIAL
 * __________________
 * 
 *  [2002] - [2017] SocialApparatus (http://SocialApparatus.co) 
 *  All Rights Reserved.
 * 
 * NOTICE:  All information contained herein is, and remains the property of SocialApparatus 
 * and its suppliers, if any.  The intellectual  and technical concepts contained herein 
 * are proprietary to SocialApparatus and its suppliers and may be covered by U.S. and Foreign 
 * Patents, patents in process, and are protected by trade secret or copyright law. 
 * 
 * Dissemination of this information or reproduction of this material is strictly forbidden 
 * unless prior written permission is obtained from SocialApparatus.
 * 
 * Contact Shane Barron admin@socia.us for more information.
 */
namespace SocialApparatus;

denyDirect();
$guid = pageArray(2);
$group = getEntity($guid);
$members = $group->members(true);
$member_string = arrayToCSSString($members);
$params = array("type" => "Activity", "metadata_name" => "owner_guid", "metadata_value" => "(" . $member_string . ")", "operand" => "IN", "order_by" => "time_created", "order_reverse" => true);
echo "<div id='groups_activity'>";
echo display("ajax/entity_list", array("params" => $params, "title" => "Group Activity", "panel" => true));