PHP写一个函数，打印出层次格式

知其黑、受其白发布时间：2021-04-25 18:55:21 ，浏览量：0

输出结果

在这里插入图片描述

题目分析

使用 pid 指向父级元素 id 是 “无限级分类” 的常用表示方法，观察题目的输出可知，这是一个深度遍历，从顶级节点开始遍历，如果某个节点下有子节点，则优先遍历子节点，直到顶级节点遍历完毕。

代码实现

在这里插入图片描述


    
        
        
        
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