Description:
------------
The expected behaviour of RecursiveArrayIterator is that only leaf nodes will be iterated, but if an array is contained by reference, it is not traversed, instead it is returned by next().

Explicit use of RecursiveIteratorIterator::LEAVES_ONLY has no affect.

Submitter has tested this in OSX and Debian Linux, others likely affected.
HHVM gives the expected result, see https://3v4l.org/up3me 


Test script:
---------------
function flatten(array $nestedArraysAndStrings){
    $flat=[];
    $iter = new RecursiveIteratorIterator(
        new RecursiveArrayIterator($nestedArraysAndStrings));
    foreach($iter as $leaf){ $flat[] = $leaf; }
    return join(NULL, $flat);
}

$noRefs = [[[['some']]],[' nested ']," items \n"];

$withRefs = []+$noRefs;
$wat = $noRefs[0];
$withRefs[0] = &$wat;

echo flatten($noRefs);
echo flatten($withRefs);

Expected result:
----------------
some nested  items n
Notice: Array to string conversion in /in/up3me on line 8
Array nested  items n

Actual result:
--------------
some nested  items 
some nested  items