php递归无限极分类

 public function getCategoryTree()
    {
        // 模拟的数据数组
        $array = [
            ['id' => 1, 'pid' => 0, 'name' => '河北省'],
            ['id' => 2, 'pid' => 0, 'name' => '北京市'],
            ['id' => 3, 'pid' => 1, 'name' => '邯郸市'],
            ['id' => 4, 'pid' => 2, 'name' => '朝阳区'],
            ['id' => 5, 'pid' => 2, 'name' => '通州区'],
            ['id' => 6, 'pid' => 4, 'name' => '望京'],
            ['id' => 7, 'pid' => 4, 'name' => '酒仙桥'],
            ['id' => 8, 'pid' => 3, 'name' => '永年区'],
            ['id' => 9, 'pid' => 1, 'name' => '武安市'],
        ];

        // 调用递归函数生成无限极分类数组
        $categories = $this->generateTree($array);

        // 直接输出JSON格式的分类数组
        return json($categories);
    }

    /**
     * 递归生成无限极分类数组
     * @param array $data 数据源
     * @param int $pid 父级ID，默认为0
     * @return array
     * 思路：     *
     * 第一次调用$data数组，得到pid=0的根节点，为其添加children子节点，将找到的根节点赋值给$tree,然后跳出循环
     * 第二次调用$data，得到pid等于根节点的子节点
     */
    private function generateTree($data, $pid = 0)
    {
        $tree = [];
        foreach ($data as $value) {
            if ($value['pid'] == $pid) {
                $value['children'] = $this->generateTree($data, $value['id']);
                $tree[] = $value;
            }
        }
        return $tree;
    }

参考文档：https://www.cnblogs.com/zxf100/p/15166921.html