<?php 
$pid= 21311;
$post = array(14564,22464,33131,44464,55646,66465,77779,88913,91231,103131,111312,12313,13131,14233,15351,161312,17132,18233,19153,20321,21311,22313,23312);
foreach($post as $k=>$v){
	if($v == $pid){
		$page = $k+1; 
		$page = $page/5;//翻页
		$page =  ceil($page);
     echo$page ;
	}
}
?>

理论上应该能实现吧不知道行不行，@cf研究一下看难不难实现