Simplify a nested array into a single level array

Question

Possible Duplicate:
How to Flatten a Multidimensional Array?

Let's say I have an array like this:

array (
  1 => 
  array (
    2 => 
    array (
      16 => 
      array (
        18 => 
        array (
        ),
      ),
      17 => 
      array (
      ),
    ),
  ),
  14 => 
  array (
    15 => 
    array (
    ),
  ),
)

How would I go about tranforming it into array like this?

array(1,2,16,18,17,14,15);

@Gordon: It is not exactly the same. In the OPs case, the values are actually the *keys*. — Felix Kling, Nov 19 '10 at 09:48

score 2 · Answer 1 · edited Feb 14 '22 at 19:57

how about some recursion

$result = array();
function walkthrough($arr){ 
    $keys = array_keys($arr);
    array_push($result, $keys);
    foreach ($keys as $key)
    {
        if (is_array($arr[$key]))
           walkthrough($arr[$key]);
        else
           array_push($result,$arr[$key]);
    }
    return $result;
}
walkthrouth($your_arr);

P.S.:Code can be bugged, but you've got an idea :)

Gordon · Accepted Answer · 2010-11-19T10:45:49.193

Sorry for the closevote. Didnt pay proper attention about you wanting the keys. Solution below:

$iterator = new RecursiveIteratorIterator(
    new RecursiveArrayIterator($arr),
    RecursiveIteratorIterator::SELF_FIRST);

$keys = array();

and then either

$keys = array();
foreach($iterator as $key => $val) {
    $keys[] = $key;
}

or with the iterator instance directly

$keys = array();
for($iterator->rewind(); $iterator->valid(); $iterator->next()) {
    $keys[] = $iterator->key();
}

or more complicated than necessary

iterator_apply($iterator, function(Iterator $iterator) use (&$keys) {
    $keys[] = $iterator->key();
    return TRUE;
}, array($iterator));

gives

Array
(
    [0] => 1
    [1] => 2
    [2] => 16
    [3] => 18
    [4] => 17
    [5] => 14
    [6] => 15
)

score 1 · Answer 3 · answered Nov 19 '10 at 08:50

1

function flattenArray($array) {
 $arrayValues = array();
 foreach (new RecursiveIteratorIterator( new RecursiveArrayIterator($array)) as $val) {
  $arrayValues[] = $val;
 }
 return $arrayValues;
} // function flattenArrayIndexed()

answered Nov 19 '10 at 08:50

Mark Baker

209,507
32
346
385

That just hides recursion. But the recursion is still there. Plus I need array keys, not values. – Richard Knop Nov 19 '10 at 09:23

score 0 · Answer 4 · answered Nov 19 '10 at 07:45

0

If we consider the nested array as a tree structure, you can apply depth first traversal to convert it into a list. That is, into a single array you desire.

answered Nov 19 '10 at 07:45

Shamim Hafiz - MSFT

21,454
43
116
176

score 0 · Answer 5 · answered Nov 19 '10 at 08:34

I have searched all similar questions and it seems there is no way without a recursion that would keep the keys order intact.

So I just went with classic recursion:

function getArrayKeysRecursive(array $theArray)
{
    $aArrayKeys = array();
    foreach ($theArray as $k=>$v) {
        if (is_array($v)) {
            $aArrayKeys = array_merge($aArrayKeys, array($k), getArrayKeysRecursive($v));
        } else {
            $aArrayKeys = array_merge($aArrayKeys, array($k));
        }
    }
    return $aArrayKeys;
}

Simplify a nested array into a single level array

5 Answers5

Linked