doxrxwn2252
2017-04-27 03:46
浏览 47
已采纳

如何在PHP / CodeIgniter中构建多维嵌套数组?

Lets say I have a table that has a record of levels that represents a tree heirarchy

id         group       parent_group_id
---------  ----------  ---------------
1          Parent 1    NULL
2          Parent 2    NULL
3          Parent 3    NULL
4          Child 1     1
5          Child 2     2
6          Child 3     2
7          Child 4     6

I need to build a recursive function to build a multidimensional nested array so that it starts out at the "top" by first building the top level arrays of rows that have parent_group_ids of NULL. Fastforward several iterations, im expecting to end up with an object like so

$result = array(
    [0] => array(
        'id' => 1,
        'group' => 'Parent 1',
        'parent_group_id' => NULL,
        'children' => array(
            [0] => array(
                'id' => 4,
                'group' => 'Child 1'
                'parent_group_id' => 1,
                'children' => NULL)),
    [1] => array(
        'id' => 2,
        'group' => 'Parent 2',
        'parent_group_id' => NULL,
        'children' => array(
            [0] => array(
                'id' => 5,
                'group' => 'Child 2'
                'parent_group_id' => 2,
                'children' => NULL),
            [1] => array(
                'id' => 6,
                'group' => 'Child 3'
                'parent_group_id' => 2,
                'children' => array(
                     [0] => array(
                         'id' => 1,
                         'group' => 'Child 4'
                         'parent_group_id' => 6,
                         'children' => NULL)))

What is the best way to build something like this? I need to ensure that it traverses down each "branch". I'm guessing when it gets the id's of the top level parents, it then proceeds to check to see if any rows exist that have a parent_group_id that equals each of the id's from the first run. Then if it finds children, gets the id's of those children and then checks again to see if children exist. And so on and so forth until it runs of out id's to check against.

I am not well-versed with foreach loops to pull off something like this.

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2条回答 默认 最新

  • duanlaiyin2356 2017-04-27 05:27
    已采纳

    Look at this source code.

    I think this function is somewhat similar to what you are asking.

      public function getAreaTree(array $elements, $parentId = null) {
        $branch = array();
    
        foreach ($elements as $element) {
    
            if ($element['parent_id'] == $parentId) {
    
                $children = getAreaTree($elements, $element['id']);
    
                if ($children) {
    
                    $element['children'] = $children;
    
                }
    
                $branch[] = $element;
            }
    
        }
    
        return empty($branch) ? null : $branch;
    }
    
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  • dskvfdxgdo2422392 2017-04-27 04:47

    Hello i had worked on same concept which you looking for..

    Use this code. It is work for me.

    function recursion($parent_id = '') {
            $categories = array();
              $this->db->from('category');
              $this->db->where('parent_id', $parent_id);
              $result = $this->db->get()->result_array();
    
              if(count($result) > 0) {
                  foreach ($result as $c) {
                    $child = $this->recursion($c['category_id']);
                    if($child) {
                        $c ['children']= $child;
                    }
                    $categories[] = $c;
                  }
              }
              return $categories;
    
        }
    
    function get_cat() {
                print_r($this->recursion());
        }
    

    This can be increased in speed for preloading all categories , thus skipping the query for each new parent_id.

    What this function does : Load all categories with a given parent_id, loop through all those categories and recursively store on array.

    But the problem is , this forces you to have a clean tree structure of your category.

    Hope it will help you for solve your problem.

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