CREATE TABLE `NewTable` (
`id` int(11) UNSIGNED NOT NULL AUTO_INCREMENT ,
`pid` int(10) UNSIGNED ZEROFILL NOT NULL ,
`name` varchar(30) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL ,
`path` varchar(200) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL ,
PRIMARY KEY (`id`)
)
ENGINE=MyISAM
DEFAULT CHARACTER SET=utf8 COLLATE=utf8_general_ci
AUTO_INCREMENT=53
CHECKSUM=0
ROW_FORMAT=DYNAMIC
DELAY_KEY_WRITE=0
;

!DOCTYPE html>
html lang="en">
head>
 meta charset="UTF-8">
 title>Document/title>
/head>
body>
 h1>四個字段的無限分類/h1>
 form action="{:url('add')}" method="post">
 請選擇上級分類：select name="pid">
 option value="0">頂級分類/option>
 {foreach $cates as $vo}
 option value={$vo.id}>|{$vo.pre}{$vo.name}/option>
 
 {/foreach}
 
 /select>br/>
 
 
 請填寫分類的名稱：input type="text" name="name"/>/br>
 input type="submit" value="添加">
 /form>
 
/body>
/html>

?php
namespace app\index\controller;
use think\Db;
use think\Controller;
use app\model\Category;
 
 
class Index extends Controller
{
 public function index()
 {
 //添加分類的界面
 //查詢所有的分類
 $db=Db::name('categroy');
 $data=$db->order('concat(path,"-",id)')->select();
 #order('concat(path,"-",id)')自動排序
 foreach ($data as $cate) {
  $prefix='';
  $i=count(explode("-", $cate['path']));
  for($n=0;$n=$i;$n++){
  $prefix.="--";
  }
  $cate['pre']=$prefix;
 }
 $this->assign('cates',$data);
 return $this->fetch();
 }
 public function add(){
 $db=Db::name('categroy');
 if($_POST['pid']==0){
  $_POST['path']=0;
 
 }else{
  $_POST['path']=$db->where('id='.$_POST['pid'])->value('path')."-".$_POST['pid']; 
 }
  $name=$_POST['name'];
 if($db->insert($_POST)){
  $this->success('添加成功');
 }else{
  $this->error('添加失敗');
 }
 #原理：4個字段
 /*
 ID PID NAME PATH
 1 0 服裝 0-1
 2 0 游戲 0-2
 3 1 男裝 0-1-3
 4 3 上衣 0-1-3-4
 */
 }}

 public function user(){
 $db=Db::name('categroy1');
 // $data=$db->getTree();
 $opt=$db->getOption($data);
 $this->assign('opt',$opt);
 $this->assign('cates',$data);
 return $this->fetch();
 }
 public function doAdd(){
 //執行添加數據
 $db=Db::name('categroy1');
 if($db->insert()){
 $this->success('添加成功',url('index'));
 }else{
 $this->error('添加失敗',url('index'));
 }
 return $this->fetch();
 }

?php
class CategoryModel extends Model{
 
 
 #通過上級分類的主鍵id號查詢子類
 public function getTree($pid=0){
 $data=$this->where('pid='.$pid)->select();
 foreach($data as $cate){
 #通過該分類的主鍵id查詢該分類的子類
 $cate['cates']=$this->getTree($cate['id']);
 }
 return $data;
 }
 
 #拼裝屬性結構
 #通過一個數組組裝option
 public function getOption($data){
 static $i=0;
 for($n=0;$n=$i*2;$n++){
 $prefix.="-";
 }
 foreach ($data as $cate) {
 $opt.="option value='".$cate['id']."'>".$prefix.$cate['name']."/option>";
 #判斷該分類下是否包含子類，如果有子類，將數組傳入接著拼裝
 if(!empty($case['cates'])){
 $i++;
 $opt.=$this->getOption($case['cases']);
 }else{
 $i=0;
 }
 return $opt;
 }
 }
}