PHP Array nested get/set

php_array_nested.php

<?php

function array_bags($keys, $root, $bags)
{
    $key = array_shift($keys);
    $root = $root[$key];

    $bags[] = ['key' => $key, 'root' => $root];

    $length = sizeof($keys);

    if ($length > 0) {
        return array_bags($keys, $root, $bags);
    } elseif ($length == 0) {
        return $bags;
    } else {
        return $root;
    }
}

function array_nested_get($keys, $root)
{
    $key = array_shift($keys);
    $root = $root[$key];

    $length = sizeof($keys);

    if ($length > 0) {
        return array_nested_get($keys, $root);
    } else {
        return $root;
    }
}

function array_nested_set($keys, $root, $value)
{
    $bags = array_bags($keys, $root, []);

    $length = sizeof($bags);
    $current = null;
    $nextKey = null;
    $previousRoot = null;

    for ($index = 0; $index < $length; $index++) {

        $current = array_pop($bags);
        $nextKey = $current['key'];

        //
        // Modification part
        //
        if ($index == 0) {
            $previousRoot = $value;
        }

        if (is_array($previousRoot)) {

            unset($previousRoot['key']);
            unset($previousRoot['root']);

            $current[$nextKey] = array_merge($current['root'], $previousRoot);
        } else {
            $current[$nextKey] = $previousRoot;
        }
        $previousRoot = $current;
    }

    unset($current['key']);
    unset($current['root']);

    $current = array_merge($root, $current);

    return $current;
}

$root = ['l1' => ['l2' => ['l3' => 'foo', 'r3' => 2], 'r2' => 1 ], 'r1' => 0];
$expect = ['l1' => ['l2' => ['l3' => 'bar', 'r3' => 2], 'r2' => 1 ], 'r1' => 0];
$key = 'l1.l2.l3';
$keys = explode('.', $key);
$bags = [];

assert('foo' == array_nested_get($keys, $root), 'array_nested_get should return foo');

$new = array_nested_set($keys, $root, 'bar');

assert($expect == $new);
assert('bar' == array_nested_get($keys, $new), 'array_nested_get should return bar');