非递归法实现论坛树型结构及分页

//更新数据库
//post.php
//begin

$content=nl2br(htmlspecialchars($content));
$title=htmlspecialchars($title); //决不允许在标题上使用html
$date=date("y-m-d h:i:s");
$length=strlen($content);

if(isset($said)) //发表新帖子
{
$query="insert into over_post

values(null,'$title','$content',$user_id,'$date',0,$length,$img,'','','')";
$result=mysql_query($query) or die(mysql_error());
$r=mysql_query("select max(id) from over_post");
$rootid = mysql_result($r,0)+0;
mysql_query("update over_post set rootid=$rootid where id=$rootid")or die(mysql_error());
}

if(isset($reply)): //发表跟帖

mysql_query("update over_post set orders=orders+1 where rootid=$rootid and orders>$orders")or

die(mysql_error());

$layer=$layer+1;
$orders=$orders+1;
$query="insert into over_post

values(null,'$title','$content',$user_id,'$date',0,$length,$img,$rootid,$orders,$layer)";

$result=mysql_query($query) or die(mysql_error());

endif;
 if($result) {
include"list.php";
}
?>
//post.php end

//重头戏，显示所有帖子，并实现分页
//list.php
//begin

//找到最新论题的rootid
$query = "select max(rootid) as maxid1, min(rootid) as minid1 from over_post";
$result = mysql_query($query);
$maxid1 = mysql_result($result, 0, "maxid1");
$startid1 = mysql_result($result, 0, "minid1");
if(!($maxid1>0)) $maxid1=0;
if(!($startid1>0)) $startid1=0;
$totalid1 = $maxid1; //这是真正的最大的rootid值, $maxid1要根据$nextmaxid1变的
if($nextmaxid1>0) $maxid1=$nextmaxid1; //翻页

//计算最小rootid:注意下面的desc,与limit结合,保证选取记录的范围.
//如果使用asc, 在mysql_result中检索第0个,将大大错误!
$itemsperpage=30;
$query="select distinct rootid from over_post where rootid

$itemsperpage";
$r=mysql_query($query);
$n=mysql_num_rows($r);
if($n>0) {
$minid1=mysql_result($r,$n-1);
$query="select * from over_post where rootid=$minid1 order by rootid

desc,orders";
$result=mysql_query($query);
$num=mysql_num_rows($result);

}
else {
$minid1=0;
$maxid1=0;
echo "

$query="select distinct rootid from over_post where rootid>$maxid1 order by rootid limit

$itemsperpage";
$r=mysql_query($query);
$n=mysql_num_rows($r);
if($n>0) $up=mysql_result($r,$n-1);
else $up=$totalid1;

$query="select distinct rootid from over_post where rootid

$itemsperpage";
$r=mysql_query($query);
$n=mysql_num_rows($r);
if($n>0) $down=mysql_result($r,0);
else $down=$maxid1;
?>

//list.php end