code: public function invalidate()
      {
          $script = escapeshellcmd($this->rootDir . "/../{$this->cacheScript}");
          $urlsFile = escapeshellarg($this->createUrlsTempFile());
          $curlTimeout = escapeshellarg($this->curlTimeout);
          // Execute in background.
          $process = new Process(sprintf('%s %s %s', $script, $urlsFile, $curlTimeout));
          $process->start();
  
          $this->resetCache();
  
          return $urlsFile;
      }
docs: Invalidates collected URLs.
  
  @return string Executed file name.