I have set $message variable. Now I wana concatenate foreach loop's results to existing $message

PHP Code:
<img style="vertical-align: text-bottom" src="<?=$user->img($folder_img$folder_altfalse'''src');?>" title="<?=$user->lang[$folder_alt];?>" alt="<?=$user->lang[$folder_alt];?>" />
            <a href="<?=$phpbb_root_path 'viewtopic.php?f=' $t['forum_id'] . '&amp;t=' $t['topic_id'] ;?>"><?=html_entity_decode($t['topic_title']);?></a><br />
My Complete code is below

PHP Code:
<?
    $message 
.= $msg\n";


    // Get active topics.
    
$sql="SELECT *
    
FROM " . TOPICS_TABLE . "
    
WHERE topic_approved '1' AND " . $db->sql_in_set('forum_id', $forums) . "
    
ORDER BY topic_last_post_time DESC";
    
$result = $db->sql_query_limit($sql,TOPICS_LIMIT);
    while (
$r = $db->sql_fetchrow($result))
    {
        
$topics[] = $r;
    }
   
$db->sql_freeresult($result);

   // How can I add "
foreach" loop's output to $message 
   
$message .= 
        
    foreach(
$topics as $t)
    {
        // Get folder img, topic status/type related information
        
$topic_tracking_info = get_complete_topic_tracking($t['forum_id'], $t['topic_id']);
        
$unread_topic = (isset($topic_tracking_info[$t['topic_id']]) && $t['topic_last_post_time'] > $topic_tracking_info[$t['topic_id']]) ? true : false;
        
$folder_img = $folder_alt = $topic_type = '';
        topic_status(
$t$t['topic_replies'], $unread_topic$folder_img$folder_alt$topic_type);
        
        // output the link
        ?>
            <img style="
vertical-aligntext-bottom" src="<?=$user->img($folder_img$folder_altfalse'''src');?>" title="<?=$user->lang[$folder_alt];?>" alt="<?=$user->lang[$folder_alt];?>" />
            <a href="<?=$phpbb_root_path 'viewtopic.php?f=' $t['forum_id'] . '&amp;t=' $t['topic_id'] ;?>"><?=html_entity_decode($t['topic_title']);?></a><br />
    <?
    
}
    
?>