Sorting and storing array returned by a method as parent and child data for displaying nested/multi level comments in codeigniter 2.0

Question

Hey guys I'm trying to learn codeigniter, but once again I'm STUCK and I seek help (as usual :P )

What I need to do?
-> I need to get the data related to a article from the database along with other stuff like the tags for the article and all the comments. I'm thinking of keeping single level nested comments for the article.

Well I'm done with the tag part [link to the answer which helped me with the same : Returning and using multidimensional array of records from database in CodeIgniter 2.0 ] but the comment part is driving me nuts.
Well to get started here is my comments table

Comments
+---------------+-------------+
| Field         | Type        |
+---------------+-------------+
| commentId     | int(10)     |
| PostId        | int(10)     |
| author        | varchar(30) |
| email         | varchar(30) |
| url           | varchar(50) |
| date          | datetime    |
| comment       | text        |
| parent        | int(10)     | 
+---------------+-------------+

I'm using the parent field to keep a track of the parent for a nested child comment. By default the value is 0 which means it the parent. Child comment will have the commentid of its parent comment

    public function getPost($postName = NULL , $year = NULL, $month = NULL ){
        if($postName != NULL && $year != NULL && $month != NULL){
            //single post
            $this->load->model('comment_model');
            $this->db->where('postName',$postName);
            $this->db->where('year(date)',$year);
            $this->db->where('month(date)',$month);
            $q = $this->db->get('mstack_Post'); 
            if($q->num_rows()>0){
                $post = $q->result();
                foreach ($post as &$p) {
                    $p->tags = $this->getAllTags($p->postId);   

                      /* getting the comments */
                    $com = $this->comment_model->getComments($p->postId); 

                    /*echo count($com).' is the total count'; output= 4 */
                    foreach ($com as &$c) {
                                      /* trying to filter the comment. but all I get is 1 comment as the output*/
                        if($c->parent==0){
                            $p->comments->parentComment = $c;
                        }elseif($c->commentId==$c->parent){
                            $p->comments->childComment = $c;
                        }
                    }
                }
                return $post;
            }else{
                return array();
            }
        }
    }

Any help will surely be appreciated. If you have any other technique /idea to display multi level comments then do let me know. :)

Answer 1

Here is the solution that might be helpfull:

First you need 2 helper recursive function:

// Building comments.
function buildComments($list, $parent = 0)
{
    // Creating result array.
    $result = array();

    //looping...
    foreach ($list as $item)
    {
        //iteration starts with 0 as default.
        if ($item->parent == $parent)
        {
            // add to the result
            $result[$item->commentId] = array(
                'author' => $item->author,
                // ... other definitions
                'child' => buildComments($list, $item->commentId) //execute this function for child.
            );
        }
    }
    return $result;
}

function printComments($arg, $depth = 1)
{
    foreach ($arg as $item)
    {
        // Printing comment...
        echo str_repeat('&nbsp; ', $depth) . $item['author'] . "<br />\r\n";
        // extra echoes...

        // if it has a child comment...
        if (count($item['child'] > 0))
        {
            printComments($item['child'], $depth + 1);
        }
    }
}

A little explaining:

The buildComments() function will starts with rows that parents has 0. Then it will execute itself for child. if child as a child, it will add it. In the end, result will be like this:

$result = array(
    1 => array(
        'author' => 'John',
        'child' => array(
            8 => array(
                'author' => 'Jane',
                'child' => array(
                    3 => array(
                        'author' => 'Jamie',
                        'child => array()
                    )
                )
            ),
            6 => array(
                'author' => 'Jackie',
                'child => array()
            ),
            9 => array(
                'author' => 'Harry',
                'child => array()
            )

        )
    ),
    4 => array(
        'author' => 'Jack',
        'child' => array()
    ),
    10 => array(
        'author' => 'Clark',
        'child' => array(
            11 => array(
                'author => 'Lois',
                'child' => array()
            )
        )
    ),
    12 => array(
        'author' => 'Luthor',
        'child' => array()
    )
);

In the printComments() function we are printing results recursive. for each child, function repeats itself. You will get result like this:

  John
    Jane
      Jamie
    Jackie
    Harry
  Jack
  Clark
    Lois
  Luthor

For more information about recursive functions Look this answer

USAGE

$this->db->where('postName',$postName);
$this->db->where('year(date)',$year);
$this->db->where('month(date)',$month);
$this->db->order_by('parent', 'asc');
$query = $this->db->get('comments');

$comments = buildComments($query->result());

printComments($comments);

that'is that simple...