php常用函数：列表转树结构

function list_to_tree($list, $root = 0,$pk = 'id', $pid = 'pid', $child = '_child') {
    // 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
            $parentId=0;
            if(isset($data[$pid])){
                $parentId =$data[$pid] ;
            }
            if ($root == $parentId) {
                $tree[] = &$list[$key];
            } else {
                if (isset($refer[$parentId])) {
                    $parent = &$refer[$parentId];
                    $parent[$child][] = &$list[$key];
                } 
            }
        } 
    }
    return $tree;
}

树转列表

function tree_to_list($tree, $level = 0,$pk = 'id', $pid = 'pid', $child = '_child'){
    $list = array();
    if (is_array($tree)){
        foreach($tree as $val) {
            $val['level']=$level;
            $child=$val['_child'];
            if(isset($child)){
                if (is_array($child)){
                    unset($val['_child']);
                    $list=$val;
                    $list = array_merge($list, tree_to_list($child,$level+1));
                }
            }else{
                $list=$val;
            }
        }
        return $list;
    }
}