我需要一个节点作为Array中的节点和叶子，具有未定义的深度

Question

I'm working on a comment system, in which one is able to reply to another comment, making it appear below the commented comment. I have a bunch of parent/child pairs, to which end I use recursion to convert this into a tree structure:

private function _create_tree_from_comments($comment_id, $entry_id) {
    $node_set = array();
    $children = $this->comment_model->get_children($comment_id, $entry_id);

    // check if we're a leaf
    if($children->num_rows() < 1) {
        return $comment_id;
    }


    foreach($children->result() as $child) {
        $node_set[$child->child] = $this->_create_tree_from_comments($child->child, $entry_id);
    }

    return $node_set;
}

Now this is all fine and well, but the problem is that I need to save information about intermediate nodes. Currently all I can do is save whatever information I need in another array at a leaf, since the intermediate nodes have responsibility to keep information about their children.

So my question is really: How am I able to save information about intermediate nodes without breaking the relationship there is between the parent and its children.

Some sample output of the function:

Array 
(
     [5] => 5
     [2] => 2
     [1] => Array
         (
               [4] => Array
                   (
                       [6] => 6
                   )

               [3] => 3
         )

)    

Answer 1

Each node in your tree could be an array like:

Array (
     ['comment_id'] => 7
     ['children'] => Array (...)
     ['whatever_else'] => 'foo'
)

So your function - instead of returning a comment ID or an array - would always return an array that contains possibly a comment id, children or empty array if no children, and anything else you wish to store

private function _create_tree_from_comments($comment_id, $entry_id) {
    $node_set = array();

    $children = $this->comment_model->get_children($comment_id, $entry_id);

    // check if we're a leaf
    if($children->num_rows() < 1) {
        $node_set['comment_id'] = $comment_id;
    }

    $node_set['children'] = array();
    foreach($children->result() as $child) {
        $node_set['children'][] = $this->_create_tree_from_comments($child->child, $entry_id);
    }

    $node_set['whatever_else'] = 'foo';

    return $node_set;
}