PHP递归实现无限级分类

 什么是无限级分类？

无限级分类是一种对商品或信息进行分类的方式，在这种分类方式中，每个分类都可以再次细分出更多的子分类，形成无限的级别

应用场景：

一个电商网站的分类可以是：服装、鞋类、家居用品等，而服装分类下又可以进一步划分成男装、女装、童装等子分类，男装分类下又可以划分成衬衫、T恤、外套等子分类，这样就形成了多层次的无限级分类

在PHP中实现无限级分类可以使用递归的方法来实现。下面是一个简单的示例： 

<?php
// 模拟分类数据
$categories = array(
    array('id' => 1, 'name' => '电子产品', 'parent_id' => 0),
    array('id' => 2, 'name' => '手机', 'parent_id' => 1),
    array('id' => 3, 'name' => '笔记本电脑', 'parent_id' => 1),
    array('id' => 4, 'name' => '家用电器', 'parent_id' => 0),
    array('id' => 5, 'name' => '电视', 'parent_id' => 4),
    array('id' => 6, 'name' => '冰箱', 'parent_id' => 4),
    array('id' => 7, 'name' => '空调', 'parent_id' => 4),
    array('id' => 8, 'name' => '服饰', 'parent_id' => 0),
    array('id' => 9, 'name' => '男装', 'parent_id' => 8),
    array('id' => 10, 'name' => '女装', 'parent_id' => 8),
    array('id' => 11, 'name' => '鞋类', 'parent_id' => 0),
    array('id' => 12, 'name' => '男鞋', 'parent_id' => 11),
    array('id' => 13, 'name' => '女鞋', 'parent_id' => 11),
    array('id' => 14, 'name' => '数码产品', 'parent_id' => 1),
    array('id' => 15, 'name' => '相机', 'parent_id' => 14),
    array('id' => 16, 'name' => '摄像机', 'parent_id' => 14),
    array('id' => 17, 'name' => '办公用品', 'parent_id' => 0),
    array('id' => 18, 'name' => '文具', 'parent_id' => 17),
    array('id' => 19, 'name' => '办公设备', 'parent_id' => 17),
    array('id' => 20, 'name' => '电脑配件', 'parent_id' => 1),
    array('id' => 21, 'name' => '显示器', 'parent_id' => 20),
    array('id' => 22, 'name' => '内存条', 'parent_id' => 20),
    array('id' => 23, 'name' => '游戏机', 'parent_id' => 1),
    array('id' => 24, 'name' => 'PS5', 'parent_id' => 23),
    array('id' => 25, 'name' => 'Switch', 'parent_id' => 23),
);
// 递归处理分类数据
function buildTree($categories, $parent_id = 0) {
    $tree = array();
    foreach ($categories as $category) {
        if ($category['parent_id'] == $parent_id) {
            $children = buildTree($categories, $category['id']);
            if ($children) {
                $category['children'] = $children;
            }
            $tree[] = $category;
        }
    }
    return $tree;
}
// 构建树形结构
$tree = buildTree($categories);
// 显示分类数据
function showTree($tree, $indent = 0) {
    foreach ($tree as $category) {
        echo str_repeat("--", $indent) . $category['name'] . "<br>";
        if (isset($category['children'])) {
            showTree($category['children'], $indent + 1);
        }
    }
}
// 调用函数显示树形结构
showTree($tree);