PHP递归函数删除所有子节点导致stackoverflow

发布于 2024-09-28 06:58:20 字数 589 浏览 5 评论 0原文

我的MySQL看起来像这样：（表的名称是类别）

'id', 'content', 'parent'

其中：

id =类别的id
内容= some-text-we-dont-care-about
Parent = 父级的 id 类别

这就是我现在正在尝试的：

function remrecurs($id) {
    $qlist=mysql_query("SELECT * FROM category WHERE parent='$id'");
    if (mysql_num_rows($qlist)>0) {
         while($curitem=mysql_fetch_array($qlist)) {
              remrecurs($curitem['parent']);
         }
    }
    mysql_query("DELETE FROM category WHERE id='$id'");
}

由于某种原因，它不起作用并且崩溃.. 知道我做错了什么吗？

原文

My MySQL looks like this: (the name of the table is category)

'id', 'content', 'parent'

where:

id = the id of the category
content =
some-text-we-dont-care-about
parent = the id of the parent
category

this is what I'm trying right now:

function remrecurs($id) {
    $qlist=mysql_query("SELECT * FROM category WHERE parent='$id'");
    if (mysql_num_rows($qlist)>0) {
         while($curitem=mysql_fetch_array($qlist)) {
              remrecurs($curitem['parent']);
         }
    }
    mysql_query("DELETE FROM category WHERE id='$id'");
}

Which for some reason doesnt work and crashes ..
Any idea what I'm doing wrong ?

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冷情 2024-10-05 06:58:20

问题出在递归调用中：

remrecurs($curitem['parent']);

它应该是：

remrecurs($curitem['id']);

为什么？

你的目标是删除具有给定 id 的行。首先，您检查它是否有任何孩子。如果是，您需要在每个子级上调用递归删除，而不是再次在父级上调用。您再次在父级上递归调用该函数。这会导致无限递归调用，您会破坏堆栈并崩溃。

The problem is in the recursive call:

remrecurs($curitem['parent']);

it should be:

remrecurs($curitem['id']);

Why?

Your objective is to delete the row with given id. First you check to see if it has any children. If yes you need to call the recursive delete on each of the children not on the parent again. You are calling the function recursively on the parent again..this leads to infinite recursive calls, you thrash the stack and crash.

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浊酒尽余欢 2024-10-05 06:58:20

或者，您可以让数据库处理这个问题。在 MySQL 中， InnoDB ON DELETE CASCADE 将自动执行此操作。

CREATE TABLE category (
    id INT PRIMARY KEY AUTO_INCREMENT,
    parent_id INT NULL,
    FOREIGN KEY (parent_id) REFERENCES category (id) ON DELETE CASCADE
) ENGINE=InnoDB

根节点应该以 NULL 作为父节点（而不是像有些人在邻接列表表上使用的那样 0）。

Alternatively, you could let the database handle this. In MySQL, an InnoDB ON DELETE CASCADE will do this automatically.

CREATE TABLE category (
    id INT PRIMARY KEY AUTO_INCREMENT,
    parent_id INT NULL,
    FOREIGN KEY (parent_id) REFERENCES category (id) ON DELETE CASCADE
) ENGINE=InnoDB

Root nodes should have NULL as parent (not 0 as some people seem to employ on Adjancency List tables).

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