code: private function __setCookieAndLocale($locale)
      {
          // @FIXME Should be refactored when cake 3.4 was released
          if (PHP_SAPI !== 'cli') {
              $time = $this->__getCookieExpireTime();
              I18n::locale($locale);
              setcookie($this->__getCookieName(), $locale, $time, '/', $this->config('Cookie.domain'));
          }
      }
docs: Set the cookie and the locale
  
  @param string $locale locale
  @return void