Simplify a nested array into a single level array [duplicate]

Answer 1

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

Answer 2

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;
}

Answer 3

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.

Answer 4

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
)

Answer 5

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 :)