类别和子类别的 PHP 树结构，无需循环查询 [英] PHP tree structure for categories and sub categories without looping a query

问题描述

我正在尝试创建一个包含任意数量子类别的类别列表，其中子类别也可以有自己的子类别.

I'm trying to create a list of categories with any number of sub categories, where sub categories can also has their own sub categories.

我已经从 Mysql 数据库中选择了所有类别，猫在一个标准的关联数组列表中，每个类别都有一个 id、名称、parentid，如果它是顶级的，那么 parentid 为 0.

I have selected all categories from the Mysql db, the cats are in a standard associate array list, each category has an id, name, parentid where the parentid is 0 if it's top level.

我基本上希望能够将猫的单级数组转换为多维数组结构，其中每个类别都可以有一个元素，该元素将包含子猫数组.

I basically want to be able to take the single level array of cats and turn it into a multidimensional array structure where each category can have an element which will contain an array of subcats.

现在，我可以通过对每个类别循环查询来轻松实现这一点，但这远非理想，我正在尝试在不影响数据库的情况下执行此操作.

Now, I can easily achieve this by looping a query for each category but this is far from ideal, I'm trying to do it without any extra hits on the db.

我知道我需要一个递归函数.任何人都可以为这种树式结构指出正确的方向吗?

I understand I need a recursive function for this. Can anyone point me in the right direction for this tree style structure?

干杯

推荐答案

这样做:

$items = array(
        (object) array('id' => 42, 'parent_id' => 1),
        (object) array('id' => 43, 'parent_id' => 42),
        (object) array('id' => 1,  'parent_id' => 0),
);

$childs = array();

foreach($items as $item)
    $childs[$item->parent_id][] = $item;

foreach($items as $item) if (isset($childs[$item->id]))
    $item->childs = $childs[$item->id];

$tree = $childs[0];

print_r($tree);

这首先通过 parent_id 对类别进行索引.然后对于每个类别，我们只需要将category->childs 设置为childs[category->id]，树就建好了！

This works by first indexing categories by parent_id. Then for each category, we just have to set category->childs to childs[category->id], and the tree is built !

所以，现在 $tree 是类别树.它包含一个 parent_id=0 的项数组，这些项本身包含一个子项数组，这些子项本身......

So, now $tree is the categories tree. It contains an array of items with parent_id=0, which themselves contain an array of their childs, which themselves ...

print_r($tree) 的输出:

stdClass Object
(
    [id] => 1
    [parent_id] => 0
    [childs] => Array
        (
            [0] => stdClass Object
                (
                    [id] => 42
                    [parent_id] => 1
                    [childs] => Array
                        (
                            [0] => stdClass Object
                                (
                                    [id] => 43
                                    [parent_id] => 42
                                )

                        )

                )

        )

)

所以这是最终的函数:

function buildTree($items) {

    $childs = array();

    foreach($items as $item)
        $childs[$item->parent_id][] = $item;

    foreach($items as $item) if (isset($childs[$item->id]))
        $item->childs = $childs[$item->id];

    return $childs[0];
}

$tree = buildTree($items);

<小时>这是带有数组的相同版本，这有点棘手，因为我们需要使用引用(但同样有效):

---

Here is the same version, with arrays, which is a little tricky as we need to play with references (but works equally well):

$items = array(
        array('id' => 42, 'parent_id' => 1),
        array('id' => 43, 'parent_id' => 42),
        array('id' => 1,  'parent_id' => 0),
);

$childs = array();
foreach($items as &$item) $childs[$item['parent_id']][] = &$item;
unset($item);

foreach($items as &$item) if (isset($childs[$item['id']]))
        $item['childs'] = $childs[$item['id']];
unset($item);

$tree = $childs[0];

所以最终函数的数组版本:

So the array version of the final function:

function buildTree($items) {
    $childs = array();

    foreach($items as &$item) $childs[(int)$item['parent_id']][] = &$item;

    foreach($items as &$item) if (isset($childs[$item['id']]))
            $item['childs'] = $childs[$item['id']];
   
    return $childs[0]; // Root only.
}

$tree = buildTree($items);

这篇关于类别和子类别的 PHP 树结构，无需循环查询的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！