PHP implements infinite pole classification _php tutorial

Unlimited pole classification for PHP

Unlimited class classification with two for loops

Table:

Field name	field Type	Notes	Default Value
Id	Int	Primary KEY Auto-increment
Name	varchar	Category name
Pid	Int	Parent class ID	0

The pid of the top category is 0 by default . When we want to take out the sub-classification tree of a classification, the basic idea is recursion , of course, for efficiency issues do not recommend querying the database every time , the general practice is to first remove all the categories, data saved in the PHP array, and then processed , and finally, the results can be cached to increase the efficiency of the next request.

Start by building an original array , which is queried directly from the database:

1. Build Your 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),);

The goal is to turn it into the following structure
Computers > Notebooks >> Super Ben >> games ben > Desktops
Mobile > Smart devices > Function machines

With an array, you can add a children key to store its sub-categories :

array(    //1对应$categories中的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)

2. Process:

$tree = array();//第一步，将所有的分类id作为数组key,并创建children单元foreach($categories as $category){    $tree[$category['id']] = $category;    $tree[$category['id']]['children'] = array();}//第二步，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 $key=>$value) {    if ($value['pid'] != 0) {        $tree[$value['pid']]['children'][] = &$tree[$key];    }}print_r($tree);

注:必须通过引用, 否则不会一次遍历就生成最终的结果.

3. Print the results as follows:

Array ([1] = = Array ([id] = 1 [name] + = computer [PID] + 0                            [Children] = = Array ([0] = = Array (                            [ID] + 3 [name] + notebook [pid] = 1                                        [Children] = = Array ([0] = = Array                                            ([id] = 7                                            [Name] = + Super ben [PID] = 3                                                [children] = = Array (                                        )) [1] = = Array         (                                   [ID] + 8 [name] + = game Ben                                                [PID] = 3 [children] = = Array                                        (                                                )                            ))) [1] = = Array (  [id] = 4 [name] + + desktop [pid] = =                        1 [children] = = Array () ))) [2] = = Array ([id] = 2 [name] =&gt ;                        Phone [PID] + 0 [children] = = Array ([0] = = Array      (                      [ID] + 5 [Name] = + Smart machine [PID] + 2                        [children] = = Array ()                            ) [1] = = Array ([id] = 6 [Name] + [PID] = 2 [children] =&gt ;     Array ()))) [3] = = Array ([id] = 3 [name] + notebook [PID] + 1 [chil                            dren] = Array ([0] = = Array (                            [id] = 7 [name] + super Ben [PID] + 3 [Children] = ArRay ()) [1] =&gt ;                            Array ([ID] + 8 [name] + = game Ben                                [PID] = 3 [children] = = Array (  ))) [4] = = Array ([id]                = 4 [name] + + desktop [PID] + 1 [children] + = Array (            )) [5] = = Array ([id] = 5 [Name] = + Smart machine [PID] + 2 [Children] = = Array ()) [6] = = Array ([id] =                > 6 [name] + [PID] = 2 [children] = = Array ( )) [7]= = Array ([id] = 7 [name] + super [PID] + 3 [children] =& Gt Array ()) [8] = = Array ([id] = 8 [name] =&G T Game Ben [PID] = 3 [Children] = Array ()))

Advantages: Clear relationship, modify the relationship between the subordinate simple.

Cons: with PHP processing, if the number of categories is large, the efficiency will be reduced.

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