code: public function clearCache()
      {
          // do not clear cache when cache directory not exists
          $cacheDir = $this->options->getCacheDir();
          if (is_null($cacheDir)) {
              throw new \Exception(sprintf(
                  'Cache directory is not configured properly.'
              ));
          }
          if (!is_dir($cacheDir) || !is_writable($cacheDir)) {
              throw new \Exception(
                  sprintf(
                      'Can not clear cache in "%s". Please be sure that directory exists and writable.',
                      $cacheDir
                  )
              );
          }
          $finder = Finder::create()
              ->in($cacheDir)
              ->ignoreDotFiles(false)
              ->name('*.php')
              ->name('.checksum')
              ->depth(0)
          ;
          try {
              $this->filesystem->remove($finder);
              return true;
          } catch (\Exception $e) {
              // just log the error
              $this->log('<error>'.$e->getMessage().'</error>');
              return false;
          }
      }
docs: Clear all cache files in cache directory.
  Only cleans cache file in path/to/yawik/var/cache/*.php.
  Files in sub cache directory will not be removed
  
  @throws \Exception when cache directory is null
  @throws \Exception when cache directory is not exists or not writable