Question

Say I have a form with these fields, and cannot rename them:

<input type="text" name="foo[bar]" />
<input type="text" name="foo[baz]" />
<input type="text" name="foo[bat][faz]" />

When submitted, PHP turns this into an array:

Array
(
    [foo] => Array
        (
            [bar] => foo bar
            [baz] => foo baz
            [bat] => Array
                (
                    [faz] => foo bat faz
                )

        )

)

What methods are there to convert or flatten this array into a data structure such as:

Array
(
    [foo[bar]] => foo bar
    [foo[baz]] => foo baz
    [foo[bat][faz]] => foo bat faz
)

Answer 1

I think this is what you want

$ritit = new RecursiveIteratorIterator(new RecursiveArrayIterator($arr));
$result = array();
foreach ($ritit as $leafValue) {
    $path = 'foo99';
    foreach (range(0, $ritit->getDepth()) as $depth) {
        $path .= sprintf('[%s]', $ritit->getSubIterator($depth)->key());
    }
    $result[$path] = $leafValue;
}

By default, RecursiveIteratorIterator only visits leaf nodes, so each iteration of the outer foreach loop has the iterator structure stopped on one of the values you care about. We find the keys that build our path to where we are by taking a peek at the iterators that RecursiveIteratorIterator is creating and managing for us(one iterator is used for each level).