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PHP+Mysql无限分类 #25

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lovecn opened this issue May 26, 2015 · 1 comment
Open

PHP+Mysql无限分类 #25

lovecn opened this issue May 26, 2015 · 1 comment

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@lovecn
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lovecn commented May 26, 2015 •
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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:category
id 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：

$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：

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：

$tree = array();
//第一步，将分类id作为数组key,并创建children单元
foreach($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：

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

id        name        pid        path
1         电脑        0          0
2         手机        0          0
3         笔记本      1          0-1
4         超级本      3          0-1-3
5         游戏本      3          0-1-3
path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。
//http://ekan001.com/article/25


class tree { 
    //访问index查看树形结构  http://www.manks.top/php-tree-deep.html
    //获取树 https://segmentfault.com/q/1010000007205669
    public static function getTree () { 
        //这里我们直接获取所有的数据，然后通过程序进行处理 
        //在无限极分类中最忌讳的是对数据库进行层层操作，也就很容易造成内存溢出 
        //最后电脑死机的结果 
        $data = $categories = array(
          array('id'=>1,'name'=>'电脑','pid'=>0),
          array('id'=>2,'name'=>'手机','pid'=>0),
          array('id'=>3,'name'=>'笔记本','pid'=>1),
          array('id'=>4,'name'=>'台式机','pid'=>1),
          array('id'=>5,'name'=>'智能机','pid'=>2),
          array('id'=>6,'name'=>'功能机','pid'=>2),
          array('id'=>7,'name'=>'超级本','pid'=>3),
          array('id'=>8,'name'=>'游戏本','pid'=>3),
      );
        return self::_generateTree($data); 
    } 
    //生成树 
    private static function _generateTree ($data, $pid = 0) { 
        $tree = []; 
        if ($data && is_array($data)) { 
            foreach($data as $v) { 
                if($v['pid'] == $pid) { 
                    $tree[] = [ 
                        'id' => $v['id'], 
                        'name' => $v['name'], 
                        'pid' => $v['pid'], 
                        'children' => self::_generateTree($data, $v['id']), 
                    ]; 
                } 
            } 
        } 
        return $tree; 
    } 
    public $cats = array();    
        
    public function category($fid=0, $level=1) {
        $sql = "SELECT * FROM `category` WHERE pid=:pid";
        $pdo = new PDO("mysql:host=localhost;dbname=test", "root", null);
        try {
            $stmt = $pdo->prepare($sql);
            $stmt -> bindParam(":pid", $fid, PDO::PARAM_INT);
            $stmt -> execute();
            $results = $stmt->fetchAll(PDO::FETCH_ASSOC);
            foreach ($results as $v) {
                array_push($this->cats, array($v['name'], $level));
                $this-> category($v['id'], $level+1, $this->cats);
                
            }

            return $this->cats;
            
        } catch(Exception $e) {
            die($e->getMessage());
        }
    }

    public function category2($fid=0, $level=1, $cats = array()) {
        $sql = "SELECT * FROM `category` WHERE pid=:pid";
        $pdo = new PDO("mysql:host=localhost;dbname=test", "root", null);
        try {
            $stmt = $pdo->prepare($sql);
            $stmt -> bindParam(":pid", $fid, PDO::PARAM_INT);
            $stmt -> execute();
            $results = $stmt->fetchAll(PDO::FETCH_ASSOC);
            foreach ($results as $v) {
                array_push($cats, array($v['name'], $level));
                $this-> category($v['id'], $level+1, $cats);
                
            }

            return $cats;
            
        } catch(Exception $e) {
            die($e->getMessage());
        }
    }
}
print_r(tree::getTree());
print_r((new tree)->category());
print_r((new tree)->category2());


/*
CREATE TABLE `category` (
 `id` int(11) NOT NULL,
 `name` varchar(50) CHARACTER SET utf8 NOT NULL,
 `pid` int(11) NOT NULL DEFAULT '0',
 PRIMARY KEY (`id`)
 )ENGINE=InnoDB DEFAULT CHARSET=utf8;
 +----+--------+-----
| id | name   | pid
+----+--------+-----
|  1 | 电脑   |   0
|  2 | 手机   |   0
|  3 | 笔记本 |   1
|  4 | 台式机 |   1
|  5 | 智能机 |   2
|  6 | 功能机 |   2
|  7 | 超级本 |   3
|  8 | 游戏本 |   3
+----+--------+-----
 */
$pdo = new PDO("mysql:host=localhost;dbname=test", "root", null);
$sql = 'SELECT * FROM `category`';
    $stmt = $pdo->prepare($sql);
    $stmt->execute();
    $data = $stmt->fetchAll(PDO::FETCH_ASSOC);
    print_r($data);
function getCategories(PDO $pdo, $pid = 0)
{
    $sql = 'SELECT * FROM `category` WHERE pid=:pid';
    $stmt = $pdo->prepare($sql);
    $stmt->bindParam(':pid', $pid, PDO::PARAM_INT);
    $stmt->execute();
    $data = $stmt->fetchAll(PDO::FETCH_ASSOC);
    foreach ($data as &$row) {
        $row['children'] = getCategories($pdo, $row['id']);
    }
    return $data;
}

$a = getCategories($pdo);
@lovecn
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lovecn commented Nov 19, 2016

https://segmentfault.com/q/1010000007523914 使用MSQL循环语句查找所有下级
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