如何使用php中的嵌套函数从所选类别中选择子类别？

Question

首先，我对此发布了另一个问题，但是没有得到答案，所以我需要发布一个新的问题。

我有一个按层次列出类别的函数，我在foreach循环中创建了另一个函数（在同一函数上），并且也将其用于下拉列表，因此不需要使用现有的多个函数来创建另一个查询。次。

我想使用相同的查询来列出所选类别下的子类别。

示例：如果单击category.php?id=100，那么我要在登录页面中列出类别100下的子类别。

这是我的职能：

$allCategories = array();
$categoryMulti = array(
    'categories' => array(),
    'parent_cats' => array()
);
while ($row = $stmt->fetch()) {
//I created another array to get subcats didnt work
//$categories['categories'][1]
    $categoryMulti['categories'][$row['cat_id']] = $row;
    $categoryMulti['parent_cats'][$row['parent_id']][] = $row['cat_id'];
    $allCategories[] = $row;
}
function listCategoryTree($parent, $category)
{
    $html = "";
    if (isset($category['parent_cats'][$parent])) {
        $html .= "<ul>\n";
        foreach

 ($category['parent_cats'][$parent] as $cat_id) {
                if (!isset($category['parent_cats'][$cat_id])) {
                    $html .= "<li>" . $category['categories'][$cat_id]['cat_name'] . "</li>";
                } else {
                    $html .= "<li>" . $category['categories'][$cat_id]['cat_name'];
                    $html .= listCategoryTree($cat_id, $category);
                    $html .= "</li>";
                }
            }
            $html .= "</ul> \n";
        }
        return $html;
    }

用法：echo listCategoryTree(0, $categoryMulti);

这是我在下拉菜单中使用的方式，仅作为示例，它可以正常工作：

function selectCategories($categories)
{
    foreach ($categories as $category) {
        echo '<option value="' . $category['cat_id'] . '">' . $category['cat_name'] . '</option>';
    }
}
selectCategories($allCategories);

这是我尝试使其与选定的类别方法一起工作的示例之一，但不幸的是，它没有工作。

我在函数中创建了一个新数组：

$subCategories = array();
$subCategories[] = $row;

并且将其作为如下函数调用，但没有用。

function cats($categories)
{
    foreach($categories as $category) {
        echo '<ul>';
        echo '<li>' . $category['cat_name'] . '</li>';
        echo '</ul>';
    }
}

echo cats(100, $subCategories);

Answer 1

有两种解决方案。首先，我将使用以下数据（categories表）作为示例。

+----+--------------------------+-----------+
| id | name                     | parent_id |
+----+--------------------------+-----------+
|  1 | Electronics              |      NULL |
|  2 | Apparel & Clothing       |      NULL |
|  3 | Phones & Accessories     |         1 |
|  4 | Computer & Office        |         1 |
|  5 | Men's Clothing           |         2 |
|  6 | Women's Clothing         |         2 |
|  7 | Cell Phones              |         3 |
|  8 | Cell Phone Accessories   |         3 |
|  9 | Phone Parts              |         3 |
| 10 | Computers & Accessories  |         4 |
| 11 | Tablets & Accessories    |         4 |
| 12 | Computer Peripherals     |         4 |
| 13 | Computer Components      |         4 |
| 14 | Office Electronics       |         4 |
+----+--------------------------+-----------+

解决方案1（Adjacency List）：

您可以使用WITH (Common Table Expressions)子句在一个查询中轻松获取类别的所有类别或子类别（需要MySQL 8.0）：

// Database connection

$options = [
    PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
    PDO::ATTR_EMULATE_PREPARES => false,
    PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
];

$pdo = new PDO('mysql:host=localhost;dbname=<DATABASE_NAME>', '<USERNAME>', '<PASSWORD>', $options);

function getCategories(PDO $db, $parentId = null)
{
    $sql = $parentId ? 'WITH RECURSIVE cte (id, name, parent_id) AS (SELECT id, name, parent_id FROM categories WHERE parent_id = ? UNION ALL SELECT c.id, c.name, c.parent_id FROM categories c INNER JOIN cte ON c.parent_id = cte.id) SELECT * FROM cte' : 'SELECT * FROM categories';
    $stmt = $db->prepare($sql);
    $stmt->execute($parentId ? [$parentId] : null);
    return $stmt->fetchAll();
}

如果您使用的是MySQL 5.7，请按如下所示更改该功能：

function getCategories(PDO $db, $parentId = null)
{
    $sql = $parentId ? 'SELECT id, name, parent_id FROM (SELECT * FROM categories ORDER BY parent_id, id) c, (select @pv := ?) initialisation WHERE find_in_set(parent_id, @pv) AND LENGTH(@pv := concat(@pv, ",", id))' : 'SELECT * FROM categories';
    $stmt = $db->prepare($sql);
    $stmt->execute($parentId ? [$parentId] : null);
    return $stmt->fetchAll();
}

要获取数据库中的所有类别：

$allCategories = getCategories($pdo);

输出：

+----+--------------------------+-----------+
| id | name                     | parent_id |
+----+--------------------------+-----------+
|  1 | Electronics              |      NULL |
|  2 | Apparel & Clothing       |      NULL |
|  3 | Phones & Accessories     |         1 |
|  4 | Computer & Office        |         1 |
|  5 | Men's Clothing           |         2 |
|  6 | Women's Clothing         |         2 |
|  7 | Cell Phones              |         3 |
|  8 | Cell Phone Accessories   |         3 |
|  9 | Phone Parts              |         3 |
| 10 | Computers & Accessories  |         4 |
| 11 | Tablets & Accessories    |         4 |
| 12 | Computer Peripherals     |         4 |
| 13 | Computer Components      |         4 |
| 14 | Office Electronics       |         4 |
+----+--------------------------+-----------+

要获取类别的子类别：

$subCategories = getCategories($pdo, 1); // 1 is parent_id

输出：

+----+--------------------------+-----------+
| id | name                     | parent_id |
+----+--------------------------+-----------+
|  3 | Phones & Accessories     |         1 |
|  4 | Computer & Office        |         1 |
|  7 | Cell Phones              |         3 |
|  8 | Cell Phone Accessories   |         3 |
|  9 | Phone Parts              |         3 |
| 10 | Computers & Accessories  |         4 |
| 11 | Tablets & Accessories    |         4 |
| 12 | Computer Peripherals     |         4 |
| 13 | Computer Components      |         4 |
| 14 | Office Electronics       |         4 |
+----+--------------------------+-----------+

如果需要HTML输出，可以循环浏览$allCategories / $subCategories（根据您的示例）：

function prepareCategories(array $categories)
{
    $result = [
        'all_categories' => [],
        'parent_categories' => []
    ];
    foreach ($categories as $category) {
        $result['all_categories'][$category['id']] = $category;
        $result['parent_categories'][$category['parent_id']][] = $category['id'];
    }
    return $result;
}

function buildCategories($categories, $parentId = null)
{
    if (!isset($categories['parent_categories'][$parentId])) {
        return '';
    }

    $html = '<ul>';
    foreach ($categories['parent_categories'][$parentId] as $cat_id) {
        if (isset($categories['parent_categories'][$cat_id])) {
            $html .= "<li><a href='#'>{$categories['all_categories'][$cat_id]['name']}</a>";
            $html .= buildCategories($categories, $cat_id);
            $html .= '</li>';
        } else {
            $html .= "<li><a href='#'>{$categories['all_categories'][$cat_id]['name']}</a></li>";
        }
    }
    $html .= '</ul>';

    return $html;
}

echo buildCategories(prepareCategories($allCategories));

输出：

echo buildCategories(prepareCategories($subCategories), 1);

输出：

解决方案2（Nested Sets）：

我们将在表中添加left和right列，并在其中添加数字以标识属于父级的组。（请注意，我们不会使用parent_id列。）

+----+--------------------------+--------------------------+
| id | name                     | parent_id | left | right |
+----+--------------------------+--------------------------+
|  1 | Electronics              |      NULL |    1 |    22 |
|  2 | Apparel & Clothing       |      NULL |   23 |    28 |
|  3 | Phones & Accessories     |         1 |    2 |     9 |
|  4 | Computer & Office        |         1 |   10 |    21 |
|  5 | Men's Clothing           |         2 |   24 |    25 |
|  6 | Women's Clothing         |         2 |   26 |    27 |
|  7 | Cell Phones              |         3 |    3 |     4 |
|  8 | Cell Phone Accessories   |         3 |    5 |     6 |
|  9 | Phone Parts              |         3 |    7 |     8 |
| 10 | Computers & Accessories  |         4 |   11 |    12 |
| 11 | Tablets & Accessories    |         4 |   13 |    14 |
| 12 | Computer Peripherals     |         4 |   15 |    16 |
| 13 | Computer Components      |         4 |   17 |    18 |
| 14 | Office Electronics       |         4 |   19 |    20 |
+----+--------------------------+--------------------------+

现在，我们需要更改功能：

function getCategories(PDO $db, $parentId = null)
{
    $sql = $parentId ? 'SELECT children.* FROM categories parent INNER JOIN categories children ON parent.left < children.left AND parent.right > children.left WHERE parent.id = ?' : 'SELECT * FROM categories';
    $stmt = $db->prepare($sql);
    $stmt->execute($parentId ? [$parentId] : null);
    return $stmt->fetchAll();
}

要获取数据库中的所有类别：

$allCategories = getCategories($pdo);

输出：

+----+--------------------------+--------------------------+
| id | name                     | parent_id | left | right |
+----+--------------------------+--------------------------+
|  1 | Electronics              |      NULL |    1 |    22 |
|  2 | Apparel & Clothing       |      NULL |   23 |    28 |
|  3 | Phones & Accessories     |         1 |    2 |     9 |
|  4 | Computer & Office        |         1 |   10 |    21 |
|  5 | Men's Clothing           |         2 |   24 |    25 |
|  6 | Women's Clothing         |         2 |   26 |    27 |
|  7 | Cell Phones              |         3 |    3 |     4 |
|  8 | Cell Phone Accessories   |         3 |    5 |     6 |
|  9 | Phone Parts              |         3 |    7 |     8 |
| 10 | Computers & Accessories  |         4 |   11 |    12 |
| 11 | Tablets & Accessories    |         4 |   13 |    14 |
| 12 | Computer Peripherals     |         4 |   15 |    16 |
| 13 | Computer Components      |         4 |   17 |    18 |
| 14 | Office Electronics       |         4 |   19 |    20 |
+----+--------------------------+--------------------------+

要获取类别的子类别：

$subCategories = getCategories($pdo, 1); // 1 is parent_id

输出：

+----+--------------------------+--------------------------+
| id | name                     | parent_id | left | right |
+----+--------------------------+--------------------------+
|  3 | Phones & Accessories     |         1 |    2 |     9 |
|  4 | Computer & Office        |         1 |   10 |    21 |
|  7 | Cell Phones              |         3 |    3 |     4 |
|  8 | Cell Phone Accessories   |         3 |    5 |     6 |
|  9 | Phone Parts              |         3 |    7 |     8 |
| 10 | Computers & Accessories  |         4 |   11 |    12 |
| 11 | Tablets & Accessories    |         4 |   13 |    14 |
| 12 | Computer Peripherals     |         4 |   15 |    16 |
| 13 | Computer Components      |         4 |   17 |    18 |
| 14 | Office Electronics       |         4 |   19 |    20 |
+----+--------------------------+--------------------------+

您可以如解决方案1中所示呈现HTML。 Read more关于在嵌套集合模型中更新和插入新数据。

来源与阅读：

如何使用php中的嵌套函数从所选类别中选择子类别？

问题描述投票：1回答：1

1个回答

解决方案1（Adjacency List）：

解决方案2（Nested Sets）：

最新问题

如何使用php中的嵌套函数从所选类别中选择子类别？

问题描述 投票：1回答：1

1个回答

解决方案1（Adjacency List）：

解决方案2（Nested Sets）：

最新问题

问题描述投票：1回答：1