无限级分类--1（商品分类）
无限级分类多用于商品的分类
其原理就是调用函数体本身，通过传递的参数不同，则查出的数据不同
无限级分类对表的设计有着要求，子类中必须有父类的id，如果是顶级分类id则父级id（parent_id）的值为0
表字段：
cat_id（自增id） cat_name（名称） parent_id（父类id）
代码实现：
//无限级分类
public function always_category($path=0)
{
$data = Db::table('category')->field(['cat_id','cat_name','parent_id'])->where(['parent_id'=>$path])->select();
foreach($data as $key=>$val)
{
$son = $this->always_category($val['cat_id']);
if(!empty($son))
{
$data[$key]['son'] = $son;
}
}
return $data;
}查出的结果格式如下：
Array
(
[0] => Array
(
[cat_id] => 28
[cat_name] => 手机、数码
[parent_id] => 0
[son] => Array
(
[0] => Array
(
[cat_id] => 29
[cat_name] => 手机通讯
[parent_id] => 28
[son] => Array
(
[0] => Array
(
[cat_id] => 30
[cat_name] => 618手机
[parent_id] => 29
)
[1] => Array
(
[cat_id] => 31
[cat_name] => 手机
[parent_id] => 29
)
[2] => Array
(
[cat_id] => 32
[cat_name] => 对讲机
[parent_id] => 29
)
)
)
[1] => Array
(
[cat_id] => 33
[cat_name] => 数码配件
[parent_id] => 28
[son] => Array
(
[0] => Array
(
[cat_id] => 34
[cat_name] => 储存卡
[parent_id] => 33
)
[1] => Array
(
[cat_id] => 35
[cat_name] => 读卡器
[parent_id] => 33
)
)
)
)
)
[1] => Array
(
[cat_id] => 36
[cat_name] => 图书、音影
[parent_id] => 0
[son] => Array
(
[0] => Array
(
[cat_id] => 38
[cat_name] => 教育
[parent_id] => 36
[son] => Array
(
[0] => Array
(
[cat_id] => 41
[cat_name] => 考试
[parent_id] => 38
)
[1] => Array
(
[cat_id] => 42
[cat_name] => 外语学习
[parent_id] => 38
)
)
)
[1] => Array
(
[cat_id] => 37
[cat_name] => 文艺
[parent_id] => 36
[son] => Array
(
[0] => Array
(
[cat_id] => 39
[cat_name] => 小说
[parent_id] => 37
)
[1] => Array
(
[cat_id] => 40
[cat_name] => 文学
[parent_id] => 37
)
)
)
)
)
[2] => Array
(
[cat_id] => 43
[cat_name] => 家用电器
[parent_id] => 0
[son] => Array
(
[0] => Array
(
[cat_id] => 44
[cat_name] => 大家电/厨房家电
[parent_id] => 43
[son] => Array
(
[0] => Array
(
[cat_id] => 45
[cat_name] => 消毒柜
[parent_id] => 44
)
)
)
[1] => Array
(
[cat_id] => 46
[cat_name] => 生活电器
[parent_id] => 43
[son] => Array
(
[0] => Array
(
[cat_id] => 47
[cat_name] => 电风扇
[parent_id] => 46
)
)
)
)
)
)一个简单的无限级分类就完成了。