associative array (JSON) to nested set (need left,right values)

Question

So I have an associative array that's been passed via JQuery to my PHP page that contains the structure of a menu. This effectively comes in as something like this:

[{"id":1,"children":[{"id":2,"children":[{"id":3},{"id":4}]},{"id":5}]}]

I've decoded the string and made it into an associative array using json_decode like so:

$cleanJSON = json_decode($JSON,true);

This is all fine so far and gives the result like this:

Array (
            [0] => Array
                (
                    [id] => 1
                    [children] => Array
                        (
                            [0] => Array
                                (
                                    [id] => 2
                                    [children] => Array
                                        (
                                            [0] => Array
                                                (
                                                    [id] => 3
                                                )
                                            [1] => Array
                                                (
                                                    [id] => 4
                                                )
                                        )
                                )
                            [1] => Array
                                (
                                    [id] => 5
                                )
                        )
                )
        )

The problem I'm having is I now need to figure out the left and right nested set values of each item so that I can update my database with this new structure.

The reason I'm doing this is to allow me to accomplish reordering menu items within the nested set model.

Getting a resulting array which looks something like the below example would be perfect:

Array (
        [0] => Array
            (
                [id] => 1
                [left] => 1
                [right] => 10
            )
        [1] => Array
            (
                [id] => 2
                [left] => 2
                [right] => 7
            )
        [2] => Array
            (
                [id] => 3
                [left] => 3
                [right] => 4
            )
        [3] => Array
            (
                [id] => 4
                [left] => 5
                [right] => 6
            )
        [4] => Array
            (
                [id] => 5
                [left] => 8
                [right] => 9
            )
    )

The below code is a mess and doesn't work at all, but it's as far as I got with it:

$i_count = 1;
$i_index = 1;
$a_newTree;

function recurseTree($nestedSet) 
{
    global $i_count;
    global $a_newTree;

    $i_left = $i_count;
    $a_newTree[$i_count-1]['left'] = $i_left;
    $i_count++;

    foreach ($nestedSet AS $key => $value)  
    {               
        if ($value['children']) 
          {
              foreach($value['children'] as $a_child)  
              {
                  recurseTree($a_child);      // traverse
              }
          }
    }   

    $i_right=$i_count; // right = count
    $a_newTree[$i_count-1]['right'] = $i_right; 
        $i_count++;        // count+1   
}

Any help appreciated!

Answer 1

SOLVED!

A nifty little function created by a friend has solved this issue for me. He actually created it in Javascript but I've translated it over to PHP. I'll supply both below.

The PHP Version first:

$JSON = '[{"id":1,"children":[{"id":2,"children":[{"id":3},{"id":4}]},{"id":5}]}]';
$cleanJSON = json_decode($JSON,true);

$a_newTree = array();       

function recurseTree($structure,$previousLeft) 
{
    global $a_newTree;  // Get global Variable to store results in.

    $indexed = array();                     // Bucket of results.       
    $indexed['id'] = $structure['id'];      // Set ID
    $indexed['left'] = $previousLeft + 1;   // Set Left

    $lastRight = $indexed['left'];

    $i_count = 0;
    if ($structure['children'])
    {
        foreach ($structure['children'] as $a_child)
        {
            $lastRight = recurseTree($structure['children'][$i_count],$lastRight);
            $i_count++;
        }
    }

    $indexed['right'] = $lastRight + 1;     // Set Right

    array_push($a_newTree,$indexed);        // Push onto stack

    return $indexed['right'];       
}

recurseTree($cleanJSON[0],0);
print_r($a_newTree);

Fantastic little function outputs the exact array required.

OK, For the original JAVASCRIPT version my friend wrote, see below:

<html>
   <head>
      <title>Experiment</title>
      <script type="text/javascript">
         /* initial structure */
         var struct = [
            {
                "id": 1,
                "children": [{
                    "id": 2,
                    "children": [{
                        "id": 3
                    }, {
                        "id": 4
                    }]
                }, {
                    "id": 5
                }]
            }
         ];

         function experiment() {
            /* stores all results */
            var all = [];

            /* kick off the recursive method */
            handleNode(struct[0], 0, all);

            /* print the results to browser debugger console*/
            console.log(all);
         }

         function handleNode(node, previousLeft, all) {
            /* create and store the new entry (bucket to put left, right, and id ) */
            var indexed = {};
            all.push(indexed);

            indexed.id = node["id"];
            indexed.left = previousLeft + 1;

            var lastRight = indexed.left;
            /* here we do the recursion for every child */
            for (var x in node["children"]) {
               lastRight = handleNode(node["children"][x], lastRight, all);
            }

            /* once all children have been iterated over we can store the rigth */
            indexed.right = lastRight + 1;

            /* return the newly updated right for this bucket */
            return indexed.right;
         }

         /* run the experiment */
         experiment();

      </script>
   </head>
   <body>

   </body>
</html>

Using Google Chrome you can see the results in the Console window. (CTRL-SHIFT-i).

Answer 2

I wouldn't try to code a Nested Set implementation yourself, there are versions available you can use:

• Nested Set PEAR package
• Nested Set extension for Doctrine