Open lovecn opened 9 years ago
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);
https://segmentfault.com/q/1010000007523914 使用MSQL循环语句查找所有下级