实现PHP+Mysql无限分类的方法汇总

无限分类是个老话题了，来看看PHP结合Mysql如何实现。

第一种方法

这种方法是很常见、很传统的一种，先看表结构

表:categoryid int 主键,自增name varchar 分类名称pid int 父类id，默认0顶级分类的 pid 默认就是0了。当我们想取出某个分类的子分类树的时候，基本思路就是递归，当然，出于效率问题不建议每次递归都查询数据库，通常的做法是先讲所有分类取出来，保存到PHP数组里，再进行处理，最后还可以将结果缓存起来以提高下次请求的效率。

先来构建一个原始数组，这个直接从数据库中拉出来就行：

复制代码 代码如下:$categories = array(    array("id"=>1,"name"=>"电脑","pid"=>0),    array("id"=>2,"name"=>"手机","pid"=>0),    array("id"=>3,"name"=>"笔记本","pid"=>1),    array("id"=>4,"name"=>"台式机","pid"=>1),    array("id"=>5,"name"=>"智能机","pid"=>2),    array("id"=>6,"name"=>"功能机","pid"=>2),    array("id"=>7,"name"=>"超级本","pid"=>3),    array("id"=>8,"name"=>"游戏本","pid"=>3),);

目标是将它转化为下面这种结构

电脑    笔记本        超级本        游戏本    台式机手机    智能机    功能机用数组来表示的话，可以增加一个 children 键来存储它的子分类：

复制代码 代码如下:array(    //1对应id，方便直接读取    1 => array(        "id"=>1,        "name"=>"电脑",        "pid"=>0,        children=>array(            &array(                "id"=>3,                "name"=>"笔记本",                "pid"=>1,                "children"=>array(                    //此处省略                )            ),            &array(                "id"=>4,                "name"=>"台式机",                "pid"=>1,                "children"=>array(                    //此处省略                )            ),        )    ),    //其他分类省略)

处理过程：

复制代码 代码如下:$tree = array();//第一步，将分类id作为数组key,并创建children单元foreach($categories as $category){    $tree[$category["id"]] = $category;    $tree[$category["id"]]["children"] = array();}//第二部，利用引用，将每个分类添加到父类children数组中，这样一次遍历即可形成树形结构。foreach ($tree as $k=>$item) {    if ($item["pid"] != 0) {        $tree[$item["pid"]]["children"][] = &$tree[$k];    }}print_r($tree);

打印结果如下：

复制代码 代码如下:Array(    [1] => Array        (            [id] => 1            [name] => 电脑            [pid] => 0            [children] => Array                (                    [0] => Array                        (                            [id] => 3                            [name] => 笔记本                            [pid] => 1                            [children] => Array                                (                                    [0] => Array                                        (                                            [id] => 7                                            [name] => 超级本                                            [pid] => 3                                            [children] => Array                                                (                                                )                                        )                                    [1] => Array                                        (                                            [id] => 8                                            [name] => 游戏本                                            [pid] => 3                                            [children] => Array                                                (                                                )                                        )                                )                        )                    [1] => Array                        (                            [id] => 4                            [name] => 台式机                            [pid] => 1                            [children] => Array                                (                                )                        )                )        )    [2] => Array        (            [id] => 2            [name] => 手机            [pid] => 0            [children] => Array                (                    [0] => Array                        (                            [id] => 5                            [name] => 智能机                            [pid] => 2                            [children] => Array                                (                                )                        )                    [1] => Array                        (                            [id] => 6                            [name] => 功能机                            [pid] => 2                            [children] => Array                                (                                )                        )                )        )    [3] => Array        (            [id] => 3            [name] => 笔记本            [pid] => 1            [children] => Array                (                    [0] => Array                        (                            [id] => 7                            [name] => 超级本                            [pid] => 3                            [children] => Array                                (                                )                        )                    [1] => Array                        (                            [id] => 8                            [name] => 游戏本                            [pid] => 3                            [children] => Array                                (                                )                        )                )        )    [4] => Array        (            [id] => 4            [name] => 台式机            [pid] => 1            [children] => Array                (                )        )    [5] => Array        (            [id] => 5            [name] => 智能机            [pid] => 2            [children] => Array                (                )        )    [6] => Array        (            [id] => 6            [name] => 功能机            [pid] => 2            [children] => Array                (                )        )    [7] => Array        (            [id] => 7            [name] => 超级本            [pid] => 3            [children] => Array                (                )        )    [8] => Array        (            [id] => 8            [name] => 游戏本            [pid] => 3            [children] => Array                (                )        ))

优点：关系清楚，修改上下级关系简单。

缺点：使用PHP处理，如果分类数量庞大，效率也会降低。

第二种方法

这种方法是在表字段中增加一个path字段：

表:categoryid int 主键,自增name varchar 分类名称pid int 父类id，默认0path varchar 路径示例数据：

id        name        pid        path1         电脑        0          02         手机        0          03         笔记本      1          0-14         超级本      3          0-1-35         游戏本      3          0-1-3path字段记录了从根分类到上一级父类的路径，用id+"-"表示。

这种方式，假设我们要查询电脑下的所有后代分类，只需要一条sql语句：

select id,name,path from category where path like (select concat(path,"-",id,"%") as path from category where id=1);结果：

+----+-----------+-------+| id | name      | path  |+----+-----------+-------+| 3  | 笔记本 | 0-1   || 4  | 超级本 | 0-1-3 || 5  | 游戏本 | 0-1-3 |+----+-----------+-------+这种方式也被很多人所采纳，我总结了下：

优点：查询容易，效率高，path字段可以加索引。

缺点：更新节点关系麻烦，需要更新所有后辈的path字段。

以上就是本文的全部内容了，两种方式，你喜欢哪种？希望大家能够喜欢。