PHP无限级分类实现

tree.php

<?php  
/** 
 * Created by PhpStorm. 
 * User: qishou 
 * Date: 15-8-2 
 * Time: 上午12:00 
 * CopyFrom: https://blog.csdn.net/qishouzhang/article/details/47204359
 */  
//准备数组，代替从数据库中检索出的数据(共有三个必须字段id,name,pid)  
header("content-type:text/html;charset=utf-8");  
$categories = array(  
    array('id'=>1,'name'=>'电脑','pid'=>0),  
    array('id'=>2,'name'=>'手机','pid'=>0),  
    array('id'=>3,'name'=>'笔记本','pid'=>1),  
    array('id'=>4,'name'=>'台式机','pid'=>1),  
    array('id'=>5,'name'=>'智能机','pid'=>2),  
    array('id'=>6,'name'=>'功能机','pid'=>2),  
    array('id'=>7,'name'=>'超级本','pid'=>3),  
    array('id'=>8,'name'=>'游戏本','pid'=>3),  
);  

/*======================非递归实现========================*/  
$tree = array();  
//第一步，将分类id作为数组key,并创建children单元  
foreach($categories as $category){  
    $tree[$category['id']] = $category;  
    $tree[$category['id']]['children'] = array();  
}  
//第二步，利用引用，将每个分类添加到父类children数组中，这样一次遍历即可形成树形结构。  
foreach($tree as $key=>$item){  
    if($item['pid'] != 0){  
        $tree[$item['pid']]['children'][] = &$tree[$key];//注意：此处必须传引用传递，循环后面的数组的改变，同样会影响此时的数组  
        if($tree[$key]['children'] == null){  
            unset($tree[$key]['children']); //如果children为空，则删除该children元素（可选）  
        }  
    }  
}  
////第三步，删除无用的非根节点数据  
foreach($tree as $key=>$category){  
    if($category['pid'] != 0){  
        unset($tree[$key]);  
    }  
}  

print_r($tree);  

/*======================递归实现========================*/  
$tree = $categories;  
function get_attr($a,$pid){  
    $tree = array();                                //每次都声明一个新数组用来放子元素  
    foreach($a as $v){  
        if($v['pid'] == $pid){                      //匹配子记录  
            $v['children'] = get_attr($a,$v['id']); //递归获取子记录  
            if($v['children'] == null){  
                unset($v['children']);             //如果子元素为空则unset()进行删除，说明已经到该分支的最后一个元素了（可选）  
            }  
            $tree[] = $v;                           //将记录存入新数组  
        }  
    }  
    return $tree;                                  //返回新数组  
}  
echo "<br/><br/><br/>";  

print_r(get_attr($tree,0));