php 实现树形结构

<?php
class Tree{
private $OriginalList;
public $pk;//主键字段名
public $parentKey;//上级id字段名
public $childrenKey;//用来存储子分类的数组key名

function __construct($pk="id",$parentKey="pid",$childrenKey="children"){
if(!empty($pk) && !empty($parentKey) && !empty($childrenKey)){
$this->pk=$pk;
$this->parentKey=$parentKey;
$this->childrenKey=$childrenKey;
}else{
return false;
}

}
//载入初始数组
function load($data){
if(is_array($data)){
$this->OriginalList=$data;
}
}

/**
* 生成嵌套格式的树形数组
* array(..."children"=>array(..."children"=>array(...)))
*/
function DeepTree($root=0){
if(!$this->OriginalList){
return FALSE;
}
$OriginalList=$this->OriginalList;
$tree=array();//最终数组
$refer=array();//存储主键与数组单元的引用关系
//遍历
foreach($OriginalList as $k=>$v){
if(!isset($v[$this->pk]) || !isset($v[$this->parentKey]) || isset($v[$this->childrenKey])){
unset($OriginalList[$k]);
continue;
}
$refer[$v[$this->pk]]=&$OriginalList[$k];//为每个数组成员建立引用关系
}
//遍历2
foreach($OriginalList as $k=>$v){
if($v[$this->parentKey]==$root){//根分类直接添加引用到tree中
$tree[]=&$OriginalList[$k];
}else{
if(isset($refer[$v[$this->parentKey]])){
$parent=&$refer[$v[$this->parentKey]];//获取父分类的引用
$parent[$this->childrenKey][]=&$OriginalList[$k];//在父分类的children中再添加一个引用成员
}
}
}
return $tree;
}
}
$data=array(
0 => array("id"=>1,"pid"=>0),
1 => array("id"=>2,"pid"=>0),
2 => array("id"=>3,"pid"=>1),
3 => array("id"=>4,"pid"=>3),
4 => array("id"=>5,"pid"=>2),
);
var_dump($data);
$tree=new Tree("id","pid","children");
$tree->load($data);
$treelist=$tree->DeepTree();//所有分类树结构
var_export($treelist);//查看结果
$subtree=$tree->DeepTree(1);//获取id为1下面的子树
var_export($subtree);
?>

转自http://www.thinkphp.cn/topic/7487.html

原文：http://www.cnblogs.com/liuwenbohhh/p/4441421.html