<?php        $data[]=array(‘id‘=>1,‘parentid‘=>0,‘name‘=>‘中国‘);      $data[]=array(‘id‘=>2,‘parentid‘=>0,‘name‘=>‘美国‘);      $data[]=array(‘id‘=>3,‘parentid‘=>0,‘name‘=>‘韩国‘);      $data[]=array(‘id‘=>4,‘parentid‘=>1,‘name‘=>‘北京‘);     $data[]=array(‘id‘=>5,‘parentid‘=>1,‘name‘=>‘上海‘);      $data[]=array(‘id‘=>6,‘parentid‘=>1,‘name‘=>‘广西‘);      $data[]=array(‘id‘=>7,‘parentid‘=>6,‘name‘=>‘桂林‘);      $data[]=array(‘id‘=>8,‘parentid‘=>6,‘name‘=>‘南宁‘);      $data[]=array(‘id‘=>9,‘parentid‘=>6,‘name‘=>‘柳州‘);     $data[]=array(‘id‘=>10,‘parentid‘=>2,‘name‘=>‘纽约‘);     $data[]=array(‘id‘=>11,‘parentid‘=>2,‘name‘=>‘华盛顿‘);     $data[]=array(‘id‘=>12,‘parentid‘=>3,‘name‘=>‘首尔‘);            $tree=build_tree($data,0);         print_r($tree);     function findChild($arr,$id){            $childs=array();   //定义一个数组          foreach ($arr as $k => $v){    //把父级二维数组遍历            if($v[‘parentid‘]== $id){     //判断子集的parentid的值是不是等于父级id的值             $childs[]=$v;                //如果等于把这个子集交给变量数组$childs            }            }            return $childs;               //返回符合条件的所有子集} function build_tree($rows,$root_id){       //$root_id父级代号          $childs=findChild($rows,$root_id);            if(empty($childs)){                        return null;            }         foreach ($childs as $k => $v){      //遍历符合父级id值的数组          $rescurTree=build_tree($rows,$v[‘id‘]);  //把子集再遍历，如果有子集就交给$rescurTree          if( null != $rescurTree){            $childs[$k][‘childs‘]=$rescurTree;  //把子集的子集交给$childs[$k][‘childs‘]，[‘childs‘]是自定义的一个键值

} } return $childs; } ?>