关于PHP的无限分类代码，网上已经有很多了，讲解的也很到位，在这里我分享一下我用着很顺手的一个

下面一段代码是创建相应数据库的sql代码：

 //////////////
   //////无限分类的数据库设计及样例
   //////////////
   mysql> create database db_kind;
   Query OK, 1 row affected

   mysql> use db_kind;
   Database changed
   mysql> create table tb_kind(
     -> id int not null auto_increment primary key,
     -> pid int,
     -> path varchar(200)
     -> );
 Query OK, 0 rows affected

 mysql> insert into tb_kind values(null,"新闻",0,0);
 Query OK, 1 row affected

 mysql> insert into tb_kind values(null,"视频",0,0);
 Query OK, 1 row affected

 mysql> insert into tb_kind values(null,"图片",0,0);
 Query OK, 1 row affected

 mysql> insert into tb_kind values(null,"博客",0,0);
 Query OK, 1 row affected

 mysql> insert into tb_kind values(null,"体育新闻",1,"0-1");
 Query OK, 1 row affected

 mysql> insert into tb_kind values(null,"娱乐新闻",1,"0-1");
 Query OK, 1 row affected

 mysql> insert into tb_kind values(null,"财经新闻",1,"0-1");
 Query OK, 1 row affected

 mysql> select * from db_kind;
 ERROR 1146 : Table 'db_kind.db_kind' doesnot exist
 mysql> select * from tb
 _kind;
 +----+----------+-----+------+
 | id | pname    | pid | path |
 +----+----------+-----+------+
 |  1 | 新闻     |   0 | 0    |
 |  2 | 视频     |   0 | 0    |
 |  3 | 图片     |   0 | 0    |
 |  4 | 博客     |   0 | 0    |
 |  5 | 体育新闻 |   1 | 0-1  |
 |  6 | 娱乐新闻 |   1 | 0-1  |
 |  7 | 财经新闻 |   1 | 0-1  |
 +----+----------+-----+------+
 7 rows in set
 mysql> insert into tb_kind values(null,"篮球新闻",5,"0-1-5");
 Query OK, 1 row affected

 mysql> insert into tb_kind values(null,"足球新闻",5,"0-1-5");
 Query OK, 1 row affected

 mysql> select * from tb_kind;
 +----+----------+-----+-------+
 | id | pname    | pid | path  |
 +----+----------+-----+-------+
 |  1 | 新闻     |   0 | 0     |
 |  2 | 视频     |   0 | 0     |
 |  3 | 图片     |   0 | 0     |
 |  4 | 博客     |   0 | 0     |
 |  5 | 体育新闻 |   1 | 0-1   |
 |  6 | 娱乐新闻 |   1 | 0-1   |
 |  7 | 财经新闻 |   1 | 0-1   |
 |  8 | 篮球新闻 |   5 | 0-1-5 |
 |  9 | 足球新闻 |   5 | 0-1-5 |
 +----+----------+-----+-------+
 9 rows in set

 mysql> insert into tb_kind values(null,"NBA",8,"0-1-5-8");
 Query OK, 1 row affected

 mysql> insert into tb_kind values(null,"CBA",8,"0-1-5-8");
 Query OK, 1 row affected

 mysql> select * from tb_kind;
 +----+----------+-----+---------+
 | id | pname    | pid | path    |
 +----+----------+-----+---------+
 |  1 | 新闻     |   0 | 0       |
 |  2 | 视频     |   0 | 0       |
 |  3 | 图片     |   0 | 0       |
 |  4 | 博客     |   0 | 0       |
 |  5 | 体育新闻 |   1 | 0-1     |
 |  6 | 娱乐新闻 |   1 | 0-1     |
 |  7 | 财经新闻 |   1 | 0-1     |
 |  8 | 篮球新闻 |   5 | 0-1-5   |
 |  9 | 足球新闻 |   5 | 0-1-5   |
 | 10 | NBA      |   8 | 0-1-5-8 |
 | 11 | CBA      |   8 | 0-1-5-8 |
 +----+----------+-----+---------+
 11 rows in set

 mysql> select concat(path,"-",id) from tb_kind;
 +---------------------+
 | concat(path,"-",id) |
 +---------------------+
 | 0-1                 |
 | 0-2                 |
 | 0-3                 |
 | 0-4                 |
 | 0-1-5               |
 | 0-1-6               |
 | 0-1-7               |
 | 0-1-5-8             |
 | 0-1-5-9             |
 | 0-1-5-8-10          |
 | 0-1-5-8-11          |
 +---------------------+
 11 rows in set

 mysql> select concat(path,"-",id) from tb_kind;
 +---------------------+
 | concat(path,"-",id) |
 +---------------------+
 | 0-1                 |
 | 0-2                 |
 | 0-3                 |
 | 0-4                 |
 | 0-1-5               |
 | 0-1-6               |
 | 0-1-7               |
 | 0-1-5-8             |
 | 0-1-5-9             |
 | 0-1-5-8-10          |
 | 0-1-5-8-11          |
 +---------------------+
 11 rows in set

 mysql> select concat(path,"-",id) as abs from tb_kind order by abs.path;
 ERROR 1054 : Unknown column 'abs.path' in 'order clause'
 mysql> select concat(path,"-",id) as abs from tb_kind order by abs

 +------------+
 | abs        |
 +------------+
 | 0-1        |
 | 0-1-5      |
 | 0-1-5-8    |
 | 0-1-5-8-10 |
 | 0-1-5-8-11 |
 | 0-1-5-9    |
 | 0-1-6      |
 | 0-1-7      |
 | 0-2        |
 | 0-3        |
 | 0-4        |
 +------------+
 11 rows in set
 mysql> select concat(path,"-",id) as,id,name,path abs from tb_kind order by abs;
 ERROR 1064 : You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'id,name,path abs from tb_kind order by abs' at line 1
 mysql> select concat(path,"-",id) as abs,
 id,pname,path abs from tb_kind order by abs;
 +------------+----+----------+---------+
 | abs        | id | pname    | abs     |
 +------------+----+----------+---------+
 | 0-1        |  1 | 新闻     | 0       |
 | 0-1-5      |  5 | 体育新闻 | 0-1     |
 | 0-1-5-8    |  8 | 篮球新闻 | 0-1-5   |
 | 0-1-5-8-10 | 10 | NBA      | 0-1-5-8 |
 | 0-1-5-8-11 | 11 | CBA      | 0-1-5-8 |
 | 0-1-5-9    |  9 | 足球新闻 | 0-1-5   |
 | 0-1-6      |  6 | 娱乐新闻 | 0-1     |
 | 0-1-7      |  7 | 财经新闻 | 0-1     |
 | 0-2        |  2 | 视频     | 0       |
 | 0-3        |  3 | 图片     | 0       |
 | 0-4        |  4 | 博客     | 0       |
 +------------+----+----------+---------+
 11 rows in set
 mysql>

下面是php源文件：

 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<title>无标题文档</title> 
</head> 
<body> 
<!--显示结果 
新闻 
体育新闻 
篮球新闻 
NBA 
CBA 
足球新闻 
娱乐新闻 
财经新闻 
视频 
图片 
博客 
--> 
<? 
$conn=mysql_connect("localhost","root","root"); 
mysql_select_db("db_kind"); 
mysql_query("set names utf8"); 
$sql="select concat(path,'-',id) as abspath,id,pname,path from tb_kind order by abspath"; 
$rs=mysql_query($sql); 
while($result=mysql_fetch_assoc($rs)){ 
$num=count(explode("-",$result[path]))-1; 
$new_str=str_repeat("---",$num); 
echo $new_str.$result[pname]; 
echo "<br>"; 
} 
$str=str_repeat("=",10); 
echo $str; 
$num=count(explode("-","0-1-5-8"))-1; 
echo $num; 
?> 
</body> 
</html> 

上面的代码中其实中间有空格的输入效果还是非常不错的，请大家本地测试。因编辑器问题导致排版混乱。