PHP - multidimensional array merge

array_merge_md.php

<?php
function array_merge_md(array &$array1, array &$array2)
{
    $merged = $array1;
    foreach ($array2 as $key => &$value) {
        if (is_array($value) && isset($merged[$key]) && is_array($merged[$key])) {
            $merged[$key] = array_merge_md($merged[$key], $value);
        } else {
            $merged[$key] = $value;
        }
    }

    return $merged;
}