Threaded App.net Conversation Into Tree

Question

I want to create a JSON tree from a flat structure - in this case an App.net Thread.

I want JSON like this

"id": "12345",
"name": "Ringo",
    "data": 
    {
        "avatar": "",
        "text": "We All Live",
    },
    "children": [{
        "id": "34567",
        "name": "John",    
        "data": 
        {
            "avatar": "",
            "text": "In a pink submarine?",
        },
        "children": [{
            "id": "35555",
            "name": "George",    
            "data": 
            {
                "avatar": "",
                "text": "Don't be daft",
            },
            "children": []
        }]
    },{
        "id": "98765",
        "name": "Paul",    
        "data": 
        {
            "avatar": "",
            "text": "In a yellow submarine?",
        },
        "children": []
    }]

So, each post can have multiple children. Each child can have children.

The JSON coming back from App.net is not threaded.

{
    "id": "98765",
    "parent": "12345"
    "details": {
    ...}
},
{
    "id": "34567",
    "parent": "12345"
    "details": {
    ...}
},

I've used json_decode() to get the JSON response in to an array. I can iterate through using foreach.

How do I put each post in the correct part of the multi dimensional array?

Parent
|_
  |-child
  |-child
  |  |-child
  |-child

etc

Answer 1

I would use references, the oft forgotten hard link of PHP. Something like this:

I'm assuming you have a $posts array that you've gotten back from an App.net API call.

(untested, may not compile / run / may have errors / may be more efficient ways to do this)

// first throw everything into an associative array for easy access
$references = array();
foreach ($posts as $post) {
    $id = $post['id'];
    $post['children'] = array();
    $references[$id] = $post;
}

// now create the tree
$tree = array();
foreach ($references as &$post) {
    $id = $post['id'];
    $parentId = $post['parent'];
    // if it's a top level object, add it to the tree
    if (!$parentId) {
        $tree[] =& $references[$id];
    }
    // else add it to the parent
    else {
        $references[$parentId]['children'][] =& $post;
    }
    // avoid bad things by clearing the reference
    unset($post);
}

// encode it
print json_encode($tree);