Fuser::getIdFromSession

static function getIdFromSession(): ?int
{
	$session = static::getSession();
	if ($session === null)
	{
		return null;
	}
	if (!$session->has(self::SESSION_USER_ID))
	{
		return null;
	}
	$rawValue = $session->get(self::SESSION_USER_ID);
	unset($session);

	$value = (int)$rawValue;
	$rawValue = (string)$rawValue;
	if ((string)$value !== $rawValue)
	{
		$value = 0;
	}

	return ($value > 0 ? $value : null);
}