code: protected function kill($pid, $signal)
      {
          $this->logger->debug("{$signal} process {$pid}");
          if (!posix_kill($pid, $signal)) {
               $this->logger->error("{$signal} process failure {$pid}");
          }
      }
docs: 杀掉单一进程
  
  @param int $pid
  @param int $signal
  @return void