Description:
------------
when recursively iterate over recursive array to alter leaves, only first leaves are altered.



Reproduce code:
---------------
$data = array ('key1' => 'val1', array('key2' => 'val2'), 'key3' => 'val3');

$iterator = new RecursiveIteratorIterator(new RecursiveArrayIterator($data));
foreach($iterator as $foo) {
    $key = $iterator->key();
    switch($key) {
        case 'key1': // first level 
        case 'key2': // recursive level
            echo "update $key<br>";
            $iterator->offsetSet($key, 'alter');
    }
}
$copy = $iterator->getArrayCopy();
var_dump($copy);

Expected result:
----------------
update key1
update key2
array(3) {
  ["key1"]=>
  string(5) "alter"
  [0]=>
  array(1) {
    ["key2"]=>
    string(4) "alter"
  }
  ["key3"]=>
  string(4) "val3"
}

Actual result:
--------------
update key1
update key2
array(3) {
  ["key1"]=>
  string(5) "alter"
  [0]=>
  array(1) {
    ["key2"]=>
    string(4) "val2"
  }
  ["key3"]=>
  string(4) "val3"
}