PHP：

<?php 
 
//連線資料庫
$connect = @mysqli_connect('','','');
if(!$connect){
    echo '資料庫連線失敗'.mysqli_error($connect);
}
mysqli_select_db( $connect, 'hairloss' );
$result = mysqli_query($connect,
						"select post_id,thread_id 
						from xf_post  
						where thread_id in(
						select thread_id from 
						(select thread_id from xf_thread 
						ORDER BY last_post_date desc LIMIT 5 ) 
						as top_five_thread_ids
						) 
						ORDER BY post_id desc;"
) or die(mysqli_error($connect));
$newMembers = [];
$i=0;
while($tr=mysqli_fetch_row($result)){
	$newMembers[$i++] = $tr[0];
}
print_r(json_encode($newMembers));
 

node_list_forum：

<div class="{$extras.last_post_id}"></div>
<a href="{{ link('posts', {'post_id': $extras.last_post_id}) }}" class="node-extra-title" title="{$extras.last_thread_title}">{$extras.last_thread_title}</a></div>
<div class="node-extra-row">
	<div style="display:none;" id="{$extras.last_post_id}">{$extras.last_post_id}</div>
	<script src="/js/vendor/jquery/jquery-3.2.1.min.js"></script>
	<script>
		$.get('/custom/latest_posts.php', function (s) {
			var latestpostsids = JSON.parse(s);
			var post_id = $('#{$extras.last_post_id}').html();
			for(var i=0;i<latestpostsids.length;i++){
				if(latestpostsids[i]== post_id){
					$(".{$extras.last_post_id}").append('<div class="new">NEW</div>');
				}
			} 
		})		
	</script>
 

最終效果圖：