code: function signalChildHandle()
      {
          $this->logger->debug("signal child handle");
  
          $this->reap();
          if (!$this->quiting && !$this->burst) {
              $this->logger->debug("child exit and spawn worker");
              $this->spawn();
          }
  
          if ($this->burst && empty($this->workers)) {
              $this->logger->debug("master process will exit");
              $this->willQuit();
              exit(0);
          }
      }
docs: SIGCHLD 信号处理器
  
  @return void