Как объединить две темы?..

$row = $db->query("SELECT posted FROM prefix_posts WHERE topic_id=$idto DESC LIMIT 1");
$arr = $db->fetch_row($row);
$timestamp = $arr['posted'];
$result = $db->query("SELECT posted FROM prefix_posts WHERE topic_id=$idfrom");
while ($row1 = $db->fetch_row($result)) {
if ($row1['posted'] < $timestamp)
$result = $db->query("UPDATE prefix_posts SET topic_id=$idto, posted=$timestamp+1 WHERE topic_id=$idfrom")
else $result = $db->query("UPDATE prefix_posts SET topic_id=$idto WHERE topic_id=$idfrom");
}

        $db->query('UPDATE '.$db->prefix.'posts SET topic_id='.$new_tid.' WHERE topic_id='.$tid) or error('Unable to update posts', __FILE__, __LINE__, $db->error());
        $db->query('UPDATE '.$db->prefix.'topics SET num_replies=(SELECT COUNT(id) FROM posts WHERE topic_id='.$new_tid.') - 1 WHERE id='.$new_tid) or error('Unable to update new topic', __FILE__, __LINE__, $db->error());
        $db->query('UPDATE '.$db->prefix.'topics SET num_replies=(SELECT COUNT(id) FROM posts WHERE topic_id='.$tid.') - 1 WHERE id='.$tid) or error('Unable to update old topic', __FILE__, __LINE__, $db->error());