Convert one dimensional array into a multi-dimensional array

Question

suppose i have this array:

Array
(
  [0] => Array
  (
    [name] => ELECTRONICS
    [depth] => 0
  )

  [1] => Array
  (
    [name] => TELEVISIONS
    [depth] => 1
  )

  [2] => Array
  (
    [name] => TUBE
    [depth] => 2
  )

  [3] => Array
  (
    [name] => LCD
    [depth] => 2
  )

  [4] => Array
  (
    [name] => PLASMA
    [depth] => 2
  )

  [5] => Array
  (
    [name] => PORTABLE ELECTRONICS
    [depth] => 1
  )
)

i want it to be converted into a multi-dimensional array such that immediate elements with a depth higher than the previous element will go inside the previous element with the key "children". like this:

Array
(
  [0] => Array
  (
    [name] => ELECTRONICS
    [depth] => 0
    [children] => Array
    (
      [0] => Array
      (
        [name] => TELEVISIONS
        [depth] => 1
        [children] => Array
        (
          [0] => Array
          (
            [name] => TUBE
            [depth] => 2
          )

          [1] => Array
          (
            [name] => LCD
            [depth] => 2
          )

          [2] => Array
          (
            [name] => PLASMA
            [depth] => 2
          )
        )
      )

      [1] => Array
      (
        [name] => PORTABLE ELECTRONICS
        [depth] => 1
      )
    )
  )
)

would greatly appreciate your help. thanks ;)

Answer 1

That was a tricky one. I'm not sure if this is the most optimal way of achieving this, but it works:

function flat_to_tree($array, $depth = 0)
{
  $out = array();
  $inCurrentDepth = true;

  foreach ($array as $key => $value) {
    if ($value['depth'] < $depth) {
      return $out;
    }

    if ($value['depth'] === $depth) {
      $inCurrentDepth = true;
      $out[] = $value;
    }

    if ($inCurrentDepth && $value['depth'] > $depth) {
      $inCurrentDepth = false;
      $out[$key - 1]['children'] = flat_to_tree(array_slice($array, $key), $value['depth']);
    }
  }

  return $out;
}

Answer 2

Here's my crack at it... Uses a foreach loop and an array of pointers to keep track of a bunch of different parent pointers.

$multi_dimensional = array();
$last_depth = 0;
$parent = &$multi_dimensional;
$parents[$last_depth] = &$parent;


foreach ($start as $idx => $data) {
  // same/increasing depth
  if ($last_depth <= $data['depth']) {
    $parent['children'][] = $data;  
  } 

  // increasing depth
  if ($last_depth < $data['depth']) {
    $parents[$last_depth] = &$parent;
  }

  // decreasing depth
  if ($last_depth > $data['depth']) {
    $parent = &$parents[$data['depth']-1];
    $parent['children'][] = $data;  
  }

  // look ahead and prepare parent in increasing
  if (isset($start[$idx+1]) && $start[$idx+1]['depth'] > $data['depth']) {
    $last_insert_idx = count($parent['children'])-1;
    $parent = &$parent['children'][$last_insert_idx];
  }
  $last_depth = $data['depth'];
}

// initial values are in child "children" array
$result = $multi_dimensional['children'];

Answer 3

I apologize for the name and the recursive nature of it. Also, notice that this function will "destroy" your original array so use a clone if you want to keep it

function multiDimensionate(&$arr, $currentLevel = 0) {
  $root = array();

  foreach ($arr as &$elem){
    if ($elem["depth"] == $currentLevel) {
      $root[] = $elem;
      unset($elem);
    } else if ($elem["depth"] == $currentLevel + 1) {
      $root[count($root)-1]["children"] = multiDimensionate($arr,$elem["depth"]);      
    }
  }

  return $root;
}

Edit: As pointed out in the coments the previous function wasnt working properly, this should be ok, still has the side effect of destroying the original array.