$usage * @param string $prefix 'ru_utime' or 'ru_stime'. * @return int|null */ private static function timevalMs(array $usage, string $prefix): ?int { $sec = $usage[$prefix . '.tv_sec'] ?? null; $usec = $usage[$prefix . '.tv_usec'] ?? null; if (!is_numeric($sec) || !is_numeric($usec)) { return null; } return (int)$sec * 1000 + intdiv((int)$usec, 1000); } }