PHP implements infinite classification (recursive method), PHP recursion_PHP tutorial

php implements infinite classification (recursive method), php recursion

I believe that many friends who learn php will try to build an online mall as a way to improve their skills. You should be comfortable with various operations on product classification, product names, etc., then you can try making unlimited classification lists.

Search the PHP Infinitus classification on the Internet. There are many, but many of them are the same. Moreover, the writing is very messy and there are a lot of codes. How do we learn? Those are not reliable, so we should tinker with Infinitus classification by ourselves. .

What is infinite classification?

Infinite-level classification is a classification technique. For example, department organization, article classification, subject classification, etc. often use infinite-level classification. It can be simply understood as classification. In fact, if we think about it carefully, there are simply too many classifications in life. Clothes can be divided into men's clothing and women's clothing, tops and pants, and they can also be classified according to age groups. Classification is everywhere, and classification appears "infinite". I won’t talk about the necessity of infinite classification here.

Introduction to the principle of infinite classification

Infinite classification may seem "high-end", but in fact the principle is very simple. Infinite classification not only requires the ingenuity of the code, but also relies on the rationality of the database design. To satisfy infinite classification, the database needs to have two necessary fields, id and pid. The id is used to identify itself, while the pid is used to indicate the parent id. In other words, each classification record not only describes itself, but also describes another ID that it is most closely concerned about. What seemed like a complicated matter was solved with such a little trick.

Without further ado, it’s time to show the examples of this article.

As an avid pirate fan, I will use the character organization of "One Piece" as an example in this article.

Database preparation:

　Build table onepiece:

create table onepiece(
  id int auto_increment,
  pid int not null,
  name varchar(225) not null,
  primary key(id)
);

　Insert test data:

insert onepiece values
  (1,0,'海军'),
  (2,0,'海贼'),
  (3,0,'革命军'),
  (4,1,'青雉'),
  (5,1,'赤犬'),
  (6,1,'黄猿'),
  (7,2,'四皇'),
  (8,2,'七武海'),
  (9,2,'草帽海贼团'),
  (10,9,'索隆'),
  (11,7,'香克斯'),
  (12,8,'多弗朗明哥'),
  (13,8,'克洛克达尔');

Here is the setting in One Piece based on popular science: the world is divided into three major camps: Navy, Pirates, and Revolutionary Army. The navy has generals: Aokiji, Akainu, and Kizaru. The pirates include: the Four Emperors, the Shichibukai, and the Straw Hat Pirates. The Four Emperors have Shanks, the Shichibukai have Doflamingo and Crocodile, and the Straw Hat Pirates have Zoro. (Advertisement: One Piece is really good).

Ultimate goal:

What we are making today are two forms of infinite classification forms, one is a drop-down list type, and the other is a navigation link type. The renderings are uploaded directly:

Drop-down list formula

Navigation Link style

　Example code:

I encapsulated an Unlimited class to call diaplayList() to display the drop-down list form, and call diaplayLink to display the navigation Link category. You can also add (addNodes()) and delete (deleteNodes) categories.

<&#63;php

class Unlimited{
  protected $mysqli;
  public function __construct($config){
    $this->mysqli=new mysqli($config['host'],$config['user'],$config['pwd']);
    $this->mysqli->select_db($config['db']);
    $this->mysqli->set_charset('utf8');
    if ($this->mysqli->connect_errno) {
      echo $this->mysqli->connect_error;
    }
  }  

  private function getList($pid=0,&$result=array(),$spac=0){
    $spac=$spac+2;
    $sql="select * from onepiece where pid={$pid}";
    $rs=$this->mysqli->query($sql);
    while($row=$rs->fetch_assoc()) {
      $row['name']=str_repeat(' &nbsp',$spac).$row['name'];
      $result[]=$row;
      $this->getList($row['id'],$result,$spac);      
    }
    return $result;
  }
  /**
   * 展现下拉列表式分类
   * @return [type] 
   */
  public function displayList(){
    $rs=$this->getList();
    $str="<select name='cate'>";

    foreach ($rs as $key => $val) {
      $str.="<option >{$val['name']}</option>";
    }
    $str.="</select>";
    return $str;
  }

  private function getLink($cid,&$result=array()){
    $sql="select * from onepiece where id={$cid}";
    $rs=$this->mysqli->query($sql);
    if($row=$rs->fetch_assoc()){
      $result[]=$row;
      $this->getLink($row['pid'],$result);
    }
    return array_reverse($result);
  }
  /**
   * 展现导航Link
   * @param [type] $cid [description]
   * @return [type]   [description]
   */
  public function displayLink($cid){
    $rs=$this->getLink($cid);
    $str='';
    foreach ($rs as $val) {
      $str.="<a href=''>{$val['name']}</a>>";
    }

    return $str;
  }
  /**
   * 增加分类
   * @param [type] $pid 父类id
   * @param [type] $name 本类名
   */
  public function addNodes($pid,$name){
    $sql="insert into onepiece values('',{$pid},'".$name."')";
    if($this->mysqli->query($sql)){

      return true;

    }
  }
  /**
   * 删除分类
   * @param [type] $id 本类id
   * @return [type]   
   */
  public function deleteNodes($id){
    $sql="select * from onepiece where pid ={$id}";
    $rs=$this->mysqli->query($sql);
    if($row=$rs->fetch_assoc()){
      $mes="还有子元素，请勿删除";
    }else{
      $sql="delete from onepiece where id={$id}";
      if($this->mysqli->query($sql)){
        $mes="删除成功";
      }
    }
    return $mes;
  }
}

The functions in the class mainly adopt the method of recursive functions. If you understand the recursive functions deeply, the rest will fall into place. I will detail the three ways to implement recursive functions in later sections.

Let’s look at another example:

First create a classification information table:

CREATE TABLE IF NOT EXISTS `category` ( 
 `categoryId` smallint(5) unsigned NOT NULL AUTO_INCREMENT, 
 `parentId` smallint(5) unsigned NOT NULL DEFAULT '0', 
 `categoryName` varchar(50) NOT NULL, 
 PRIMARY KEY (`categoryId`) 
) ; 

Insert some data:

INSERT INTO `category` (`categoryId`, `parentId`, `categoryName`) VALUES 
(1, 0, 'php'), 
(2, 0, 'java'), 
(3, 0, 'c/c++'), 
(4, 1, 'php基础'), 
(5, 1, 'php开源资料'), 
(6, 1, 'php框架'), 
(7, 2, 'java Se'), 
(8, 2, 'java EE'), 
(9, 2, 'java Me'), 
(10, 3, 'c/c++基础编程'), 
(11, 3, 'c/c++系统开发'), 
(12, 3, 'c嵌入式编程'), 
(13, 3, 'c++应用开发'), 
(14, 13, 'c++桌面应用开发'), 
(15, 13, 'c++游戏开发'); 

The following is the php code:

<&#63;php 
/* 
php无限极分类 
*/ 
 
//获取某分类的直接子分类 
function getSons($categorys,$catId=0){ 
  $sons=array(); 
  foreach($categorys as $item){ 
    if($item['parentId']==$catId) 
      $sons[]=$item; 
  } 
  return $sons; 
} 
 
//获取某个分类的所有子分类 
function getSubs($categorys,$catId=0,$level=1){ 
  $subs=array(); 
  foreach($categorys as $item){ 
    if($item['parentId']==$catId){ 
      $item['level']=$level; 
      $subs[]=$item; 
      $subs=array_merge($subs,getSubs($categorys,$item['categoryId'],$level+1)); 
       
    } 
       
  } 
  return $subs; 
} 
 
//获取某个分类的所有父分类 
//方法一，递归 
function getParents($categorys,$catId){ 
  $tree=array(); 
  foreach($categorys as $item){ 
    if($item['categoryId']==$catId){ 
      if($item['parentId']>0) 
        $tree=array_merge($tree,getParents($categorys,$item['parentId'])); 
      $tree[]=$item;  
      break;  
    } 
  } 
  return $tree; 
} 
 
//方法二,迭代 
function getParents2($categorys,$catId){ 
  $tree=array(); 
  while($catId != 0){ 
    foreach($categorys as $item){ 
      if($item['categoryId']==$catId){ 
        $tree[]=$item; 
        $catId=$item['parentId']; 
        break;  
      } 
    } 
  } 
  return $tree; 
} 

//测试 部分 
$pdo=new PDO('mysql:host=localhost;dbname=test','root','8888'); 
$stmt=$pdo->query("select * from category order by categoryId"); 
$categorys=$stmt->fetchAll(PDO::FETCH_ASSOC); 
 
$result=getSons($categorys,1); 
foreach($result as $item) 
  echo $item['categoryName'].'<br>'; 
echo '<hr>'; 
 
$result=getSubs($categorys,0); 
foreach($result as $item) 
  echo str_repeat(' ',$item['level']).$item['categoryName'].'<br>'; 
echo '<hr>'; 
 
$result=getParents($categorys,7); 
foreach($result as $item) 
  echo $item['categoryName'].' >> '; 
echo '<hr>'; 
 
$result=getParents2($categorys,15); 
foreach($result as $item) 
  echo $item['categoryName'].' >> '; 
&#63;> 

Let’s take a look at the final result

Although this article introduces infinite classification using recursion, in fact, it is not recommended for everyone to do so. Everyone knows that the more classifications, the less efficient the recursion will be. This article is just to make everyone better. This is done by understanding recursion.

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