PHP deep clone and recursive array merge

<?php
function deep_clone(mixed $value): mixed
{
    return unserialize(serialize($value));
}

function deep_merge(array $base, array $override): array
{
    foreach ($override as $key => $value) {
        if (is_array($value) && isset($base[$key]) && is_array($base[$key])) {
            $base[$key] = deep_merge($base[$key], $value);
        } else {
            $base[$key] = deep_clone($value);
        }
    }
    return $base;
}