我想制作一个bootstrap 4导航菜单，我有以下SQL查询，下面有一些代码，但我无法理解如何做到这一点！
这些是表格
TABLE menu
--------------------------------------
| id | title | url |
| 1 | Home | index.php |
| 2 | Menu | # |
| 3 | Contact | # |
| 2 | Winkelwagen | winkelwagen.php |
--------------------------------------
TABLE categories
-------------------------------------
| id | title_cat | url | cparent_id |
| 1 | Auto's | # | 2 |
| 2 | Drank | # | 2 |
-------------------------------------
TABLE products
-------------------------------------
| id | product | url | pparent_id |
| 1 | Ferrari | # | 1 |
| 2 | Heineken | # | 2 |
-------------------------------------
以下是查询：
$query = "SELECT
X.level,
X.id,
X.name,
X.url,
X.parent_id
FROM
(
SELECT
1 AS LEVEL,
id AS id,
title AS NAME,
url AS url,
0 AS parent_id,
id AS id_1,
-1 AS id_2,
-1 AS id_3
FROM
menu
WHERE
1
UNION
SELECT
2 AS LEVEL,
id AS id,
title_cat AS NAME,
url AS url,
cparent_id AS parent_id,
cparent_id AS id_1,
id AS id_2,
-1 AS id_3
FROM
categories
WHERE
1
UNION
SELECT
3 AS LEVEL,
products.id AS id,
products.product AS NAME,
products.url AS url,
products.pparent_id AS parent_id,
categories.cparent_id AS id_1,
categories.id AS id_2,
products.id AS id_3
FROM
products
LEFT JOIN categories ON products.pparent_id = categories.id
WHERE
1
) X
WHERE
1
ORDER BY
id_1,
id_2,
id_3";
这给下面的表提供了级别（我也添加了parent_id，但是parent_id buildTree($array)进入循环）：
level id name url parent_id
1 1 Home index.php 0
1 2 Menu # 0
2 1 Auto's # 2
3 1 Ferrari # 1
2 2 Drank # 2
3 2 Heineken # 2
1 3 Contact contact.php 0
1 4 Winkelwagen winkelwagen.php 0
我希望导航菜单看起来像这样：
<li class="nav-item">
<a class="nav-link" href="index.php">Home</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Menu</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<div class="dropdown-submenu">
<a class="dropdown-item dropdown-toggle" href="#">Auto's</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Ferrari</a>
</div>
</div>
<div class="dropdown-submenu">
<a class="dropdown-item dropdown-toggle" href="#">Drank</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Heineken</a>
</div>
</div>
</div>
</li>
<li class="nav-item">
<a class="nav-link" href="#">Contact</a>
</li>
<li class="nav-item">
<a class="nav-link" href="winkelwagen.php">Winkelwagen</a>
</li>
我有以下代码，首先我们从上面提到的查询中创建一个数组：
$sql = $pdo->prepare($query);
function menu_builder($sql) {
if ($sql->execute()) {
while ($row = $sql->fetch(PDO::FETCH_ASSOC)) {
$array[] = $row;
}
buildTree($array); // or menu_builder($sql);
}
}
下一个代码不起作用，因为它进入无限循环（如果它有效，我仍然需要使html正确：）：
function buildTree($array, $parent_id = 0, $parents = array()) {
if($parent_id == 0) {
foreach ($array as $element) {
if (($element['parent_id'] != 0) && !in_array($element['parent_id'], $parents)) {
$parents[] = $element['parent_id'];
}
}
}
$menu_html = '';
foreach($array as $element) {
if($element['parent_id'] == $parent_id) {
if(in_array($element['id'], $parents)) {
$menu_html .= '<li class="dropdown">';
$menu_html .= '<a href="'.$element['url'].'" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-expanded="false">'.$element['name'].' <span class="caret"></span></a>';
}
else {
$menu_html .= '<li>';
$menu_html .= '<a href="' . $element['url'] . '">' . $element['name'] . '</a>';
}
if(in_array($element['id'], $parents)) {
$menu_html .= '<ul class="dropdown-menu" role="menu">';
$menu_html .= buildTree($array, $element['id'], $parents);
$menu_html .= '</ul>';
}
$menu_html .= '</li>';
}
}
return $menu_html;
}
这个菜单生成了一个正常的<ul> / <li>菜单，我不知道如何通过bootstrap让它为我工作：
function menu_builder($sql) {
$level = 0;
if ($sql->execute()) {
while ($row = $sql->fetch(PDO::FETCH_ASSOC)) {
while($level < $row['level']) {
echo "<ul>" . PHP_EOL;
$level++;
}
while($level > $row['level']) {
echo "</ul>" . PHP_EOL;
$level--;
}
echo " <li>#" . $row['id'] . "->" . $row['name'] . "</li>" . PHP_EOL;
}
}
while($level-- > 0) {
echo "</ul>" . PHP_EOL;
}
}
如果您需要更多信息，请问我，我尝试使用我尝试的代码和我正在使用的表格尽可能清楚地提出问题。
jQuery的：
$('.dropdown-menu a.dropdown-toggle').on('click', function(e) {
if (!$(this).next().hasClass('show')) {
$(this).parents('.dropdown-menu').first().find('.show').removeClass("show");
}
var $subMenu = $(this).next(".dropdown-menu");
$subMenu.toggleClass('show');
$(this).parents('li.nav-item.dropdown.show').on('hidden.bs.dropdown', function(e) {
$('.dropdown-submenu .show').removeClass("show");
});
return false;
});
CSS：
.dropdown-submenu {
position: relative;
}
.dropdown-submenu a::after {
transform: rotate(-90deg);
position: absolute;
right: 6px;
top: .8em;
}
.dropdown-submenu .dropdown-menu {
top: 0;
left: 100%;
margin-left: .1rem;
margin-right: .1rem;
}
答案 0 :(得分：1)
我认为使这一点变得困难的一部分是尝试将创建数据结构和表示结合起来。通常最好先构建数据，然后再担心如何呈现数据。
尽我所能，我尽力将其分解为单独的步骤。我添加了一些注释掉的print_r语句，以便您可以看到每个步骤正在做什么。如果您对此有任何疑问，请与我们联系。
#!/usr/bin/php
<?php
// The query results
$results = [
// Level, id, title, link, parent
[1, 1, 'Home', 'index.php', 0],
[1, 2, 'Menu', '#', 0],
[2, 1, "Auto's", '#', 2],
[3, 1, 'Ferrari', '#', 1],
[2, 2, 'Drank', '#', 2],
[3, 2, 'Heineken', '#', 2],
[1, 3, 'Contact', 'contact.php', 0],
[1, 4, 'Winkelwagen', 'winkelwagen.php', 0],
];
// creates a constant for the query result row keys (you should avoid using a global constant for this)
define('KEYS', ['level', 'id', 'title', 'link', 'parent_id']);
// adds the keys to each result row (this is just to help readability/maintainability)
$rows = array_map(function (array $item): stdClass {
// cast this as an object so we don't have to use pass by reference later (I think this improves readability).
return (object)array_combine(KEYS, $item);
}, $results);
// uncomment to see raw $rows
//print_r($rows);die;
// creates a key for each row based on the level and id (this way they will be unique)
$keys = array_map(function (stdClass $row): string {
$key = "$row->level-$row->id";
$row->key = $key;
return $key;
}, $rows);
$keyed = array_combine($keys, $rows);
// uncomment to see $keyed values
//print_r($keyed);die;
// converts the keyed records into a tree.
$tree = [];
foreach($keyed as $item) {
if (1 === $item->level) {
$tree[] = $item;
continue;
}
$parent = ($item->level - 1).'-'.$item->parent_id;
if (!isset($keyed[$parent])) {
throw new Exception("could not find parent element '$parent'");
}
$keyed[$parent]->children[] = $item;
}
// uncomment to see $tree structure
//print_r($tree);die;
?>
<!-- add ul classes for style -->
<ul>
<?php foreach ($tree as $trunk): ?>
<?php if (!isset($trunk->children)): ?>
<li class="nav-item">
<a class="nav-link" href="<?=$trunk->link?>"><?=$trunk->title?></a>
</li>
<?php else: ?>
<li class="nav-item dropdown">
<!-- id attributes must be unique so we add the item key to the end of it to make it unique-->
<a class="nav-link dropdown-toggle" role="button"
href="<?=$trunk->link?>" id="navbarDropdown<?=$trunk->key?>"
data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"><?=$trunk->title?></a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<?php foreach ($trunk->children as $branch): ?>
<?php if (!isset($branch->children)): ?>
<!-- add style to this if needed -->
<a href="<?=$branch->link?>"><?=$branch->title?></a>
<?php else: ?>
<div class="dropdown-submenu">
<a class="dropdown-item dropdown-toggle" id="navbarDropdown<?=$branch->key?>"
href="<?=$branch->link?>"><?=$branch->title?></a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown<?=$branch->key?>">
<!-- You may need to add some additional style code to this for it to work with multiple items -->
<?php foreach ($branch->children as $leaf): ?>
<a class="dropdown-item" href="<?=$branch->link?>"><?=$branch->title?></a>
<?php endforeach; ?>
</div>
</div>
<?php endif ?>
<?php endforeach; ?>
</div>
</li>
<?php endif ?>
<?php endforeach ?>
</ul>
根据经验，我尽量避免使用嵌套循环，但在这种情况下，每个级别似乎都有单独的样式。如果你想让它能够处理超过三个级别，你可能想要考虑使用递归函数。
答案 1 :(得分：1)
我已经采用了比递归buildTree更线性的方法。这种方式更容易一些，因为需要根据树的级别输出不同的HTML。我为您的数据创建了SQLFiddle，并添加了一些额外的值以用于测试目的。查询发生变化，以便我可以查看菜单项是否具有子菜单以及该子菜单是否包含产品，所有这些都在一行中：
SELECT m.title AS title, m.url AS m_url,
c.title_cat AS title_cat, c.url AS c_url,
p.product AS product, p.url AS p_url
FROM menu m
LEFT JOIN categories c
ON c.cparent_id = m.id
LEFT JOIN products p
ON p.pparent_id = c.id
ORDER BY m.id, c.id, p.id
此查询的输出（基于扩展数据）是：
title m_url title_cat c_url product p_url
Home index.php (null) (null) (null) (null)
Menu # Auto's # Ferrari www.ferrari.com
Menu # Auto's # Maserati #
Menu # Drank # Heineken #
Menu # Food # (null) (null)
Second Menu # Hotels # The Ritz www.ritzparis.com
Contact contact.php (null) (null) (null) (null)
Winkelwagen winkelwagen.php (null) (null) (null) (null)
基本查询调用保持不变，虽然不是获取所有数据然后处理它，而是获取数据并同时处理它。
$sql = $pdo->prepare($query);
$sql->execute() or die("Unable to execute query!");
buildTree($sql);
buildTree例程。我认为这些评论相当不言自明，但基本上它遍历每一行数据，并确定是否需要依次创建新菜单项，新子菜单或新子菜单项。
function buildTree($sql) {
$thisTitle = '';
$thisCategory = '';
while ($element = $sql->fetch(PDO::FETCH_ASSOC)) {
if (!$element['c_url']) {
// simple top element
// do we need to close any prior menus?
if ($thisCategory != '') {
echo " </div>\n </div>\n";
$thisCategory = '';
}
if ($thisTitle != '') {
echo "</li>\n";
$thisTitle = '';
}
echo <<<EOD
<li class="nav-item">
<a class="nav-link" href="{$element['m_url']}">{$element['title']}</a>
</li>
EOD;
}
else {
// got a category
// do we need a new menu item?
if ($element['title'] != $thisTitle) {
// is it the first menu item? if not, need to close the previous one
if ($thisTitle != '') {
// do we also need to close a previous category menu?
if ($thisCategory != '') {
echo " </div>\n </div>\n";
$thisCategory = '';
}
echo "</li>\n";
}
$thisTitle = $element['title'];
echo <<<EOD
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="{$element['m_url']}" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">$thisTitle</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
EOD;
}
// do we need a new submenu?
if ($element['title_cat'] != $thisCategory) {
// is it the first submenu? if not, need to close the previous one
if ($thisCategory != '') echo " </div>\n";
$thisCategory = $element['title_cat'];
// create a submenu
echo <<<EOD
<div class="dropdown-submenu">
<a class="dropdown-item dropdown-toggle" href="{$element['c_url']}">$thisCategory</a>
EOD;
}
// is there a product?
if ($element['p_url']) {
// create a product menu item
echo <<<EOD
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="{$element['p_url']}">{$element['product']}</a>
</div>
EOD;
}
}
}
}
扩展数据的此代码输出为：
<li class="nav-item">
<a class="nav-link" href="index.php">Home</a>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Menu</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<div class="dropdown-submenu">
<a class="dropdown-item dropdown-toggle" href="#">Auto's</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="www.ferrari.com">Ferrari</a>
</div>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Maserati</a>
</div>
</div>
<div class="dropdown-submenu">
<a class="dropdown-item dropdown-toggle" href="#">Drank</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="#">Heineken</a>
</div>
</div>
<div class="dropdown-submenu">
<a class="dropdown-item dropdown-toggle" href="#">Food</a>
</div>
</div>
</li>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false">Second Menu</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<div class="dropdown-submenu">
<a class="dropdown-item dropdown-toggle" href="#">Hotels</a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="www.ritzparis.com">The Ritz Paris</a>
</div>
</div>
</div>
</li>
<li class="nav-item">
<a class="nav-link" href="contact.php">Contact</a>
</li>
<li class="nav-item">
<a class="nav-link" href="winkelwagen.php">Winkelwagen</a>
</li>
答案 2 :(得分：0)
试试这个
<?php
$servername = "localhost";
$username = "root";
$password = "";
try {
$pdo = new PDO("mysql:host=$servername;dbname=testing", $username, $password);
// set the PDO error mode to exception
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
} catch (PDOException $e) {
echo "Connection failed: " . $e->getMessage();
}
$querySubmenu = "SELECT a.id, a.title, a.url, b.title_cat AS cat_name, b.url AS cat_url, c.product AS product_name, c.url AS product_url FROM menu a
JOIN (SELECT * FROM categories) b ON a.id = b.cparent_id
JOIN (SELECT * FROM products) c ON b.id = c.pparent_id";
$queryMenu = "SELECT a.*, 0 AS cat_name, 0 AS cat_url, 0 AS product_name, 0 AS product_url FROM menu a WHERE id NOT IN (
SELECT a.id FROM menu a
JOIN (SELECT * FROM categories) b ON a.id = b.cparent_id
JOIN (SELECT * FROM products) c ON b.id = c.pparent_id)";
$sqlMenu = $pdo->prepare($queryMenu);
$sqlSubmenu = $pdo->prepare($querySubmenu);
$menu = menu_builder($sqlMenu);
$submenu = menu_builder($sqlSubmenu);
$arr = array_merge($menu, $submenu);
usort($arr, function ($a, $b) {
return $a['id'] - $b['id'];
});
function menu_builder($sql)
{
if ($sql->execute()) {
while ($row = $sql->fetch(PDO::FETCH_ASSOC)) {
$array[] = $row;
}
return $array;
}
}
foreach ($arr as $element) {
if ($element['cat_name'] == '0') { ?>
<li class="nav-item">
<a class="nav-link" href="<?php echo $element['url'] ?>"><?php echo $element['title'] ?></a>
</li>
<?php }
if ($element['cat_name'] != '0') { ?>
<li class="nav-item dropdown">
<a class="nav-link dropdown-toggle" href="#" id="navbarDropdown" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"><?php echo $element['title'] ?></a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<div class="dropdown-submenu">
<a class="dropdown-item dropdown-toggle" href="<?php echo $element['cat_url'] ?>"><?php echo $element['cat_name'] ?></a>
<div class="dropdown-menu" aria-labelledby="navbarDropdown">
<a class="dropdown-item" href="<?php echo $element['product_url'] ?>"><?php echo $element['product_name'] ?></a>
</div>
</div>
</div>
</li>
<?php }
}
?>