Symfony\Component\HttpFoundation\Request::getScriptName PHP Method

    public function getScriptName()
    {
        return $this->server->get('SCRIPT_NAME', $this->server->get('ORIG_SCRIPT_NAME', ''));
    }

 /**
  * Determines if redirect may be performed.
  *
  * @param Request $request
  *   The current request object.
  * @param string $route_name
  *   The current route name.
  *
  * @return bool
  *   TRUE if redirect may be performed.
  */
 public function canRedirect(Request $request, $route_name = NULL)
 {
     $can_redirect = TRUE;
     if (isset($route_name)) {
         $route = $this->routeProvider->getRouteByName($route_name);
         if ($this->config->get('access_check')) {
             // Do not redirect if is a protected page.
             $can_redirect = $this->accessManager->checkNamedRoute($route_name, [], $this->account);
         }
     } else {
         $route = $request->attributes->get(RouteObjectInterface::ROUTE_OBJECT);
     }
     if (strpos($request->getScriptName(), 'index.php') === FALSE) {
         // Do not redirect if the root script is not /index.php.
         $can_redirect = FALSE;
     } elseif (!($request->isMethod('GET') || $request->isMethod('HEAD'))) {
         // Do not redirect if this is other than GET request.
         $can_redirect = FALSE;
     } elseif ($this->state->get('system.maintenance_mode') || defined('MAINTENANCE_MODE')) {
         // Do not redirect in offline or maintenance mode.
         $can_redirect = FALSE;
     } elseif ($this->config->get('ignore_admin_path') && isset($route)) {
         // Do not redirect on admin paths.
         $can_redirect &= !(bool) $route->getOption('_admin_route');
     }
     return $can_redirect;
 }