code: private function purgeSymfonyCache(): void
      {
          $filesystem = new Filesystem();
          $cacheDir = $this->getContainerParameter('kernel.cache_dir');
          $ref = new \ReflectionObject($this->container);
          $containerDir = basename(\dirname($ref->getFileName()));
  
          /** @var SplFileInfo[] $finder */
          $finder = Finder::create()
              ->depth(0)
              ->exclude($containerDir)
              ->in($cacheDir)
          ;
  
          foreach ($finder as $file) {
              $filesystem->remove($file->getPathname());
          }
  
          if (\function_exists('opcache_reset')) {
              opcache_reset();
          }
  
          if (\function_exists('apc_clear_cache') && !ini_get('apc.stat')) {
              apc_clear_cache();
          }
      }
docs: The method preserves the container directory inside the cache folder,
  because Symfony will throw a "compile error" exception if it is deleted
  in the middle of a request.