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

问题描述

我试图创建的类别列表与任意数量的子类，其中的子类别也可以拥有自己的子类。

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.

我选择了从MySQL数据库的所有类别中，猫是在一个标准的关联数组列表，每个类别都有一个ID，姓名，PARENTID其中PARENTID为0，如果是顶级水准。

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.

基本上，我希望能够把猫的单级阵列，把它变成一个多维数组结构，其中每一类可以其中将包含subcats的数组中的元素。

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，我可以很容易地通过循环为每个类别查询实现这一目标，但这是很不理想，我想这样做不会对数据库的任何额外命中。

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.

我明白我需要为这个递归函数。任何人都可以点我在正确的方向为这​​棵树式结构？

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

这做这项工作：

$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);

这通过首先检索类别由PARENT_ID。然后对于每个类别中，我们只需要设置类别 - ＆GT;孩子的到童车[类别 - ＆GT; ID] ，和树建！

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 $树是类别树。它包含与PARENT_ID = 0项的阵列，它们本身包含其孩子的，这本身...

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 ...

的print_r的输出（$树）：

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
                                )

                        )

                )

        )

)

因此​​，这里是最后的功能：

So here is the final function:

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);

---

这里是同一个版本，使用数组，这是一个有点棘手，因为我们需要参考玩（但同样适用）：

---

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];

所以最终的功能的阵列版本：

So the array version of the final function:

function buildTree($items) {

    $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']];

    return $childs[0];
}

$tree = buildTree($items);

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