若是QQ空间那种，这里无需再使用无限级分类。

而是帖子之下的评论回复使用字段标记分清从属后按时间排序就行

//根据回复评论表，查询出回复人和被回复人信息

select
acrr.id,comment_id,content,time,acrr.account_id,type,mi.name as mename,mi.p_w_picpath as mimg,
do.name as doname,do.p_w_picpath as dimg,replied_account_id,rtype,(select name from ll_member_info where account_id=replied_account_id) as rmename,
(select name from ll_doctor_info where account_id=replied_account_id) as rdoname,
(select p_w_picpath from ll_member_info where account_id=replied_account_id) as rmimg,
(select p_w_picpath from ll_doctor_info where account_id=replied_account_id) as rdimg
from
ll_article_comment_reply_record as acrr
left join ll_member_info as mi on acrr.account_id=mi.account_id
left join ll_doctor_info as do on acrr.account_id=do.account_id
where
article_id=$article_id
AND comment_id=$cid
order by time asc

无限级分类：一个分类型可以有无限个分类

常见的无限分类实现

商品分类，子类导航，贴吧回帖

//=====1.递归方式实现无限级分类======

原理：每个分类都需记录它的父级id，当为顶级分类时，父级id为0.每个分类都可通过父级id一层层查明它所在父级，以便知道它所属分类，层级深度为几。

递归——自己调用自身（一定要有判断）？

储存结果的变量迭代方法

总结：

self::getList($row['id'],$result,$spac);不断递归pid

$sql='select * from imooc where pid='.$pid;不断按需要调整条件查询

function getList($pid=0,&$result=array(),$spac=0)  $result[]=$row;不断迭代

当使用迭代去除所有数据时，是怎样区分ta分级的。

getList($pid=0,&$result=array(),$spac=0)

用这个表示区分层数，每次调用都是new出新栈独立运算

//=====2.全路径无限分类：以一个字段把它所有父级ID按顺序记录下来=====

总结：

$sql="select id,catename,path,concat(path,',',id) as fullpath from imooc order by fullpath asc";

他在order by的时候就已经将序列搞好了

区分深度

$deep=count(explode(',', trim($row['fullpath'],',')));

///无限级分类_代码展示

<?
/** Author:Abo* Date:2015/7/27*/
/*
变成下拉列表
从pid=0递归下去
*/
class toList{public static $mysqli;function conn(){$mysqli=new mysqli('localhost','root','','test');$mysqli->query('set names utf8');if(!$mysqli) die("连接数据库失败".$mysqli->connect_error());return $mysqli;}function getList($pid=0,&$result=array(),$spac=0){$spac=$spac+4;$mysqli=self::conn();$sql='select * from imooc where pid='.$pid;$res=$mysqli->query($sql);while ($row=$res->fetch_assoc()) {$row['catename']=str_repeat(' ', $spac).'|--'.$row['catename'];$result[]=$row;self::getList($row['id'],$result,$spac);             //递归}return $result;if($mysqli!=null) $mysqli->close();}
}
/*
按要求封装数据，变成下拉列表
*/
function displayCate($pid = 0, $selected = 0) {$ts = new toList ();$ts->conn ();$rs = $ts->getList ();$temp=null;$str="<select name='cate'>";foreach ( $rs as $val ) {$temp=null;if($val['id']==$selected){echo $val['id'];$temp="selected='selected'";}    $str.="<option $temp >".$val ['catename'].'</option>';}$str.='</select>';return $str;
}
header("Content-Type: text/html;charset=utf8");
echo displayCate(0,2);/*
变成导航栏
从pid=10递归上来再倒序
*/
class toList{public $host='localhost';public $username='root';public $password='';public $db='test';function conn(){$mysqli=new mysqli($this->host,$this->username,$this->password,$this->db);$mysqli->query('set names utf8');if(!$mysqli) die('数据库连接失败'.$mysqli->connect_error);return $mysqli;    }function getList($id,&$result=array()){$sql='select * from imooc where id='.$id;$mysqli=self::conn();$res=$mysqli->query($sql);if($row=$res->fetch_assoc()){$result[]=$row;self::getList($row['pid'],$result);}return $result;}
}$ts=new toList();
$rs=$ts->getList(10);
/*
按要求封装变成地址导航
*/echo krsort($rs);header("Content-Type: text/html;charset=utf8");
echo '<pre>';
print_r($rs);//===============================全路径无限分类==================================
/*
下拉列表
*/
class toList{public $host='localhost';public $username='root';public $password='';public $db='test';function conn(){$mysqli=new mysqli($this->host,$this->username,$this->password,$this->db);$mysqli->query('set names utf8');if(!$mysqli) die('数据库连接失败'.$mysqli->connect_error);return $mysqli;}function getList(){$sql="select id,catename,path,concat(path,',',id) as fullpath from imooc order by fullpath asc";$mysqli=self::conn();$res=$mysqli->query($sql);$result=array();while($row=$res->fetch_assoc()){$deep=count(explode(',', trim($row['fullpath'],',')));$row['catename']=str_repeat(' ', $deep).'|--'.$row['catename'];    $result[]=$row;
//             self::getList($row['pid'],$result);}return $result;}
}$ts=new toList();
$rs=$ts->getList();header("Content-Type: text/html;charset=utf8");
$str="<select name='cate'>";
foreach ($rs as $val){$str.='<option>'.$val['catename'].'<option>';
}
$str.="</select>";echo $str;class toList{public $host='localhost';public $username='root';public $password='';public $db='test';function conn(){$mysqli=new mysqli($this->host,$this->username,$this->password,$this->db);$mysqli->query('set names utf8');if(!$mysqli) die('数据库连接失败'.$mysqli->connect_error);return $mysqli;}function getList($cateid){$sql="select * ,concat(path,',',id) fullpath from imooc where id= $cateid";$mysqli=self::conn();$res=$mysqli->query($sql);$row=$res->fetch_assoc();$ids = $row['fullpath'];$sql="select * from imooc where id in ($ids) order by id asc";$res=$mysqli->query($sql);$result=array();while($row=$res->fetch_assoc()){$deep=count(explode(',', trim($row['fullpath'],',')));$row['catename']=str_repeat(' ', $deep).'|--'.$row['catename'];    $result[]=$row;
//             self::getList($row['pid'],$result);}return $result;}
}$ts=new toList();
$rs=$ts->getList(4);
echo '<pre>';
print_r($rs);
header("Content-Type: text/html;charset=utf8");
// $str="<select name='cate'>";
/*
按要求封装变成地址导航
*/
foreach ($rs as $val){echo "<a href=''>".$val['catename']."</a>>";
}