从数组列表创建数组树

哦，这就是我解决的方法：

$arr = array(  array('id'=>100, 'parentid'=>0, 'name'=>'a'),  array('id'=>101, 'parentid'=>100, 'name'=>'a'),  array('id'=>102, 'parentid'=>101, 'name'=>'a'),  array('id'=>103, 'parentid'=>101, 'name'=>'a'),);$new = array();foreach ($arr as $a){    $new[$a['parentid']][] = $a;}$tree = createTree($new, array($arr[0]));print_r($tree);function createTree(&$list, $parent){    $tree = array();    foreach ($parent as $k=>$l){        if(isset($list[$l['id']])){ $l['children'] = createTree($list, $list[$l['id']]);        }        $tree[] = $l;    }     return $tree;}