无限级分类

一、递归

//递归
//树形的类
class Tree
{
    protected $data;
    public $treeList;
    public function __construct()
    {
        $catalog= new Catalog();//实例化分类的model
        $this->data=$catalog->show();//将要分类的数据查询出来
        $this->treeList=$this->tree($result,0,0);//构造中就执行了分类方法
    }
    /**
    * $result为存放数据的空数组
    * $pid 为数据表字段中的pid 初始为0 顶级类别先查询
    * $spac 为计数器
    */
    public function tree(&$result=array(),$pid,$spac){
        $spac=$spac+4;
        foreach($this->data as $value){
            if($value['p_id']==$pid){
                $value['catalog_name'] = str_repeat(' ',$spac)."|--".$value['catalog_name'];
                $result[] = $value;
                unset($value); //把这个节点从数组中移除,减少后续递归消耗
                $this->tree($result,$value['catalog_id'],$spac);
            }
        }
        return $result;
    }
}
//其他界面调用的代码
$tree=new Tree();
$tree_list=$tree->treeList;

二、引用

//假设这是我们数据库查询出来的数据（二维数组）
$arr=[
    [
        'tid' =>  1,
        'tname' =>  '亚洲',
        'p_id' =>0],
    [
        'tid' =>  2,
        'tname' =>  '欧洲' ,
        'p_id' =>  0],
    [
        'tid' => 3,
        'tname' => '非洲' ,
        'p_id' =>  0],
    [
        'tid' =>  4,
        'tname' => '中国',
        'p_id' => 1],
    [
        'tid' => 5,
        'tname' => '美洲',
        'p_id' => 0],
    [
        'tid' =>  6,
        'tname' =>  '台湾',
        'p_id' => 4],
    [
        'tid' =>  7,
        'tname' => '墨西哥' ,
        'p_id' =>  5]
];
function generateTree($array){
    //第一步 构造数据 为上面的数组加上索引
    $items = array();
    foreach($array as $value){
        $items[$value['tid']] = $value;
    }
    //第二步 遍历数据 生成树状结构
    $tree = array();
    foreach($items as $key => &$value){
        if(isset($items[$value['p_id']])){
            $items[$value['p_id']]['son'][] = &$value;
        }else{
            $tree[] = &$value;
        }
        //如果还涉及到另外一张表，另一张表的id与分类表的id一样时
        //将分类和标签结合
        //foreach($tags as $k=>$v){
          //if ($v['catalog_id']==$value['catalog_id']){
            //$value['tags'][]=$v;
          //}
        //}
    }
    return $tree;
}
//测试代码
$list=generateTree($arr);
print_r($list);
//测试的结果
Array
(
    [0] => Array
        (
            [tid] => 1
            [tname] => 亚洲
            [p_id] => 0
            [son] => Array
                (
                    [0] => Array
                        (
                            [tid] => 4
                            [tname] => 中国
                            [p_id] => 1
                            [son] => Array
                                (
                                    [0] => Array
                                        (
                                            [tid] => 6
                                            [tname] => 台湾
                                            [p_id] => 4
                                        )
                                )
                        )
                )
        )
    [1] => Array
        (
            [tid] => 2
            [tname] => 欧洲
            [p_id] => 0
        )
    [2] => Array
        (
            [tid] => 3
            [tname] => 非洲
            [p_id] => 0
        )
    [3] => Array
        (
            [tid] => 5
            [tname] => 美洲
            [p_id] => 0
            [son] => Array
                (
                    [0] => Array
                        (
                            [tid] => 7
                            [tname] => 墨西哥
                            [p_id] => 5
                        )
                )
        )
)

拓展：根据标签查找所属的父级分类（pid=0）

2张表（分类表和标签表）

sp_type 分类表 —tid —tname 分类名称 —p_id 父级id

sp_tags 标签表 —tag_id —tag_name 标签名称 —tid 对应的分类表id

需求：传入tag_id 数组，查询对应的分类表最顶级分类 p_id=0

$tag = input('');
$tags_res = Db::name('tags')
            ->where('tag_id', 'in', $tag['tags_id'])
            ->join('sp_type', 'sp_type.tid=sp_tags.tid')
            ->select();
//最初结果
array (size=2)
  0 => 
    array (size=5)
      'tag_id' => int 2
      'tag_name' => string '非洲大草原' (length=15)
      'tid' => int 2
      'tname' => string '非洲' (length=6)
      'p_id' => int 0
  1 => 
    array (size=5)
      'tag_id' => int 7
      'tag_name' => string '泉州' (length=6)
      'tid' => int 6
      'tname' => string '福建' (length=6)
      'p_id' => int 20
----------------------------------------------------------------------
    for ($i = 0; $i < count($tags_res); $i++) {
        $res[] = $this->getZero($tags_res[$i]);
    }
    public function getZero($param)
    {
        $type = Db::name('type')->select();
        while (true) {
            if ($param['p_id'] == 0) {
                return $param;
            }
            foreach ($type as $key => $value) {
                if ($value['tid'] == $param['p_id']) {
                    $param=[
                        'tid'=>$value['tid'],
                        'tname'=>$value['tname'],
                        'tag_name'=>$param['tag_name'],
                        'p_id'=>$value['p_id']
                    ];
                    continue;
                }
            }
        }
    }
//执行结果,获得传入的标签数组对应的分类数组的顶级分类
array (size=2)
  0 => 
    array (size=5)
      'tag_id' => int 2
      'tag_name' => string '非洲大草原' (length=15)
      'tid' => int 2
      'tname' => string '非洲' (length=6)
      'p_id' => int 0
  1 => 
    array (size=4)
      'tid' => int 1
      'tname' => string '亚洲' (length=6)
      'tag_name' => string '泉州' (length=6)
      'p_id' => int 0