RecursiveArrayIterator example

array_iterator.php

<?php 

$configs = [
    'test' => [
        'alfa' => 'beta'
    ],
    'gamma' => 'first'
];

$iterator = new \RecursiveArrayIterator($configs);
$iteratorIterator = new \RecursiveIteratorIterator($iterator, \RecursiveIteratorIterator::SELF_FIRST);

$config = [];

foreach ($iteratorIterator as $key => $value) {
    if ($iteratorIterator->getDepth() == 0) {
        unset($levelKey);
        $levelKey[0] = "config_".$key;
    }

    if ($iteratorIterator->getDepth() > 0 && $iteratorIterator->callHasChildren()) {
        $levelKey[$iteratorIterator->getDepth()] = $levelKey[$iteratorIterator->getDepth() - 1]."_".$key;
    } else if ($iteratorIterator->getDepth() > 0 && !$iteratorIterator->callHasChildren()) {
        $config[$levelKey[$iteratorIterator->getDepth()-1]."_".$key] = $value;
    } else if ($iteratorIterator->getDepth() == 0 && !$iteratorIterator->callHasChildren()) {
        $config[$levelKey[$iteratorIterator->getDepth()]] = $value;
    }
}