Standard sorting
ArrayObject Object
(
    [storage:ArrayObject:private] => Array
        (
            [3] => img1.png
            [1] => img10.png
            [0] => img12.png
            [2] => img2.png
        )

    [flags:ArrayObject:private] => 0
    [iteratorClass:ArrayObject:private] => ArrayIterator
)

Natural order sorting
ArrayObject Object
(
    [storage:ArrayObject:private] => Array
        (
            [3] => img1.png
            [2] => img2.png
            [1] => img10.png
            [0] => img12.png
        )

    [flags:ArrayObject:private] => 0
    [iteratorClass:ArrayObject:private] => ArrayIterator
)