實現PHP+Mysql無限分類的方法匯總
Jun 13, 2016 am 09:13 AM
實現PHP+Mysql無限分類的方法匯總
?這篇文章主要給大家匯總介紹了實現PHP+Mysql無限分類的2種方法，并對比分析了2種方法的優(yōu)劣,需要的朋友可以參考下
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無限分類是個老話題了，來看看PHP結合Mysql如何實現。
第一種方法
這種方法是很常見、很傳統(tǒng)的一種，先看表結構
表:category
id int 主鍵,自增
name varchar 分類名稱
pid int 父類id，默認0
頂級分類的 pid 默認就是0了。當我們想取出某個分類的子分類樹的時候，基本思路就是遞歸，當然，出于效率問題不建議每次遞歸都查詢數據庫，通常的做法是先講所有分類取出來，保存到PHP數組里，再進行處理，最后還可以將結果緩存起來以提高下次請求的效率。
先來構建一個原始數組，這個直接從數據庫中拉出來就行：
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代碼如下:
$categories = array(
array('id'=>1,'name'=>'電腦','pid'=>0),
array('id'=>2,'name'=>'手機','pid'=>0),
array('id'=>3,'name'=>'筆記本','pid'=>1),
array('id'=>4,'name'=>'臺式機','pid'=>1),
array('id'=>5,'name'=>'智能機','pid'=>2),
array('id'=>6,'name'=>'功能機','pid'=>2),
array('id'=>7,'name'=>'超級本','pid'=>3),
array('id'=>8,'name'=>'游戲本','pid'=>3),
);
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目標是將它轉化為下面這種結構
電腦
筆記本
超級本
游戲本
臺式機
手機
智能機
功能機
用數組來表示的話，可以增加一個 children 鍵來存儲它的子分類：
?
代碼如下:
array(
//1對應id，方便直接讀取
1 => array(
'id'=>1,
'name'=>'電腦',
'pid'=>0,
children=>array(
&array(
'id'=>3,
'name'=>'筆記本',
'pid'=>1,
'children'=>array(
//此處省略
)
),
&array(
'id'=>4,
'name'=>'臺式機',
'pid'=>1,
'children'=>array(
//此處省略
)
),
)
),
//其他分類省略
)
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處理過程：
?
代碼如下:
$tree = array();
//第一步，將分類id作為數組key,并創(chuàng)建children單元
foreach($categories as $category){
$tree[$category['id']] = $category;
$tree[$category['id']]['children'] = array();
}
//第二部，利用引用，將每個分類添加到父類children數組中，這樣一次遍歷即可形成樹形結構。
foreach ($tree as $k=>$item) {
if ($item['pid'] != 0) {
$tree[$item['pid']]['children'][] = &$tree[$k];
}
}
print_r($tree);
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打印結果如下：
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代碼如下:
Array
(
[1] => Array
(
[id] => 1
[name] => 電腦
[pid] => 0
[children] => Array
(
[0] => Array
(
[id] => 3
[name] => 筆記本
[pid] => 1
[children] => Array
(
[0] => Array
(
[id] => 7
[name] => 超級本
[pid] => 3
[children] => Array
(
)
)
[1] => Array
(
[id] => 8
[name] => 游戲本
[pid] => 3
[children] => Array
(
)
)
)
)
[1] => Array
(
[id] => 4
[name] => 臺式機
[pid] => 1
[children] => Array
(
)
)
)
)
[2] => Array
(
[id] => 2
[name] => 手機
[pid] => 0
[children] => Array
(
[0] => Array
(
[id] => 5
[name] => 智能機
[pid] => 2
[children] => Array
(
)
)
[1] => Array
(
[id] => 6
[name] => 功能機
[pid] => 2
[children] => Array
(
)
)
)
)
[3] => Array
(
[id] => 3
[name] => 筆記本
[pid] => 1
[children] => Array
(
[0] => Array
(
[id] => 7
[name] => 超級本
[pid] => 3
[children] => Array
(
)
)
[1] => Array
(
[id] => 8
[name] => 游戲本
[pid] => 3
[children] => Array
(
)
)
)
)
[4] => Array
(
[id] => 4
[name] => 臺式機
[pid] => 1
[children] => Array
(
)
)
[5] => Array
(
[id] => 5
[name] => 智能機
[pid] => 2
[children] => Array
(
)
)
[6] => Array
(
[id] => 6
[name] => 功能機
[pid] => 2
[children] => Array
(
)
)
[7] => Array
(
[id] => 7
[name] => 超級本
[pid] => 3
[children] => Array
(
)
)
[8] => Array
(
[id] => 8
[name] => 游戲本
[pid] => 3
[children] => Array
(
)
)
)
?
優(yōu)點：關系清楚，修改上下級關系簡單。
缺點：使用PHP處理，如果分類數量龐大，效率也會降低。
第二種方法
這種方法是在表字段中增加一個path字段：
表:category
id int 主鍵,自增
name varchar 分類名稱
pid int 父類id，默認0
path varchar 路徑
示例數據：
id name pid path
1 電腦 0 0
2 手機 0 0
3 筆記本 1 0-1
4 超級本 3 0-1-3
5 游戲本 3 0-1-3
path字段記錄了從根分類到上一級父類的路徑，用id+'-'表示。
這種方式，假設我們要查詢電腦下的所有后代分類，只需要一條sql語句：
select id,name,path from category where path like (select concat(path,'-',id,'%') as path from category where id=1);
結果：
+----+-----------+-------+
| id | name | path |
+----+-----------+-------+
| 3 | 筆記本 | 0-1 |
| 4 | 超級本 | 0-1-3 |
| 5 | 游戲本 | 0-1-3 |
+----+-----------+-------+
這種方式也被很多人所采納，我總結了下：
優(yōu)點：查詢容易，效率高，path字段可以加索引。
缺點：更新節(jié)點關系麻煩，需要更新所有后輩的path字段。
以上就是本文的全部內容了，兩種方式，你喜歡哪種？希望大家能夠喜歡。
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