Database Unlimited Classification How to get all sub-categories under the category with the category ID, the above table structure

CAT_ID cat_name pid Cat_pat
Category ID (self-increment) category name 0 (parent ID, if 0 is the root category, the self-increment ID) path
May I ask you the great God, can give the best method, directly with the category ID 1 to query out all the following sub-categories
The data table is as follows:

ID cat_name PID Cat_path
1 Mobile 0,
2 Smartphones 1, 1,
3 Samsung 2, 1, 2,
4 Samsung S Series 3,
5 Samsung M Series 3,.

Reply content:

CAT_ID cat_name pid Cat_pat
Category ID (self-increment) category name 0 (parent ID, if 0 is the root category, the self-increment ID) path
May I ask you the great God, can give the best method, directly with the category ID 1 to query out all the following sub-categories
The data table is as follows:

ID cat_name PID Cat_path
1 Mobile 0,
2 Smartphones 1, 1,
3 Samsung 2, 1, 2,
4 Samsung S Series 3,
5 Samsung M Series 3,.

No one answered, there was a job that had been done a while ago, to give you the algorithm.
The idea is as follows: use a stack to temporarily save the unhandled root node and all its child nodes, constantly take a node input from the stack, and put its immediate child nodes, pressing onto the stack until the stack is empty and the algorithm ends.
I have rewritten the detailed comments for you, to understand that should not be a problem!

    $waitList = array();                     //等待堆栈（数组用做堆栈），未处理的id    array_push($waitList, $_GET["cid"]);     //我这是点中某个节点（cid），列出所有子类中的数据    $rsList = array();                        //结果队列    while (count($waitList) > 0) {            //等待堆栈中还有节点，继续处理        $tmp = array_pop($waitList);          //取出一个节点        array_push($rsList, $tmp);            //输出这个节点        $dc = M("DocCategory");               //从数据表中找出这个节点的所有子节点        $dcon['pid'] = $tmp;        $dcs = $dc->where($dcon)->field('id')->select();        foreach ($dcs as $value) {                //将所有子节点压入等待堆栈            array_push($waitList, $value['id']);        }    }    $con['category'] = array('in', $rsList);      //生成查询条件，等待队列中已经包含了所有的子节点

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