php7将二维数组转为树状数组

    public function list_to_tree($list, $pk=‘id‘, $pid = ‘pid‘, $child = ‘children‘, $root = 0) {
    //创建Tree
        $tree = array();
     
        if (is_array($list)) {
            //创建基于主键的数组引用
            $refer = array();
     
            foreach ($list as $key => $data) {
                $refer[$data[$pk]] = &$list[$key];
            }
     
            foreach ($list as $key => $data) {
                //判断是否存在parent
                $parantId = $data[$pid];
     
                if ($root == $parantId) {
                    $tree[] = &$list[$key];
                } else {
                    if (isset($refer[$parantId])) {
                        $parent = &$refer[$parantId];
                        $parent[$child][] = &$list[$key];
                    }
                }
            }
        }