duanliaolan6178 2014-07-09 20:57
浏览 127
已采纳

PHP pcntl_fork()背后会发生什么?

I have spend hours, days, weeks trying to understand how PHP pcntl really works and still dont know exactly what is really happening.

Why parents and childs ? I am using Debian (am far for being an expert in computers I must admit) but all I want to do is receive a message from my webSocket client (which I have already managed to do) and keep listening other users.

In other words, if I receive a message and use a sleep(5); then the server will not listen any other messages until this piece of code is finished.

Note that the sleep(5) is for test purposes. I plan to process hundreds of messages simultaneously and thats why am trying to figure out how could pcntl be helpfull.

$pid = pcntl_fork();

echo "start
";

if($pid) {
  // parent process runs what is here
  echo "parent
";
}
else {
  // child process runs what is here
  echo "child
";
}

echo "end
";

What exactly is happening behind the above script ? Why am I getting this result ?

start

parent

end

start

child

end

Could someone please explain me what is the computer "thinking" ?

展开全部

  • 写回答

1条回答 默认 最新

  • donglang1976 2014-07-09 21:11
    关注

    This is basically what happens:

                        pcntl_fork()
                           ||
          +----------------++------------------+
        parent                               child
    
        "start"                              ...
        "parent"                             ...
        "end"                                ...
                                             "start"
                                             "child"
                                             "end"
    

    Any code after pcntl_fork() gets executed by both parent and child process; you can think of the child as a clone of the parent, except that the outcome of pcntl_fork() is 0; it's like the code enters a different reality, not unlike Back to the future ;-)

    This is just one of the possible outcomes, though; depending on cpu usage, the child's "start" may occur together with the parent's "parent" output.

    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论
编辑
预览

报告相同问题?

悬赏问题

  • ¥15 在更新角色衣服索引后,Sprite 并未正确显示更新的效果该如何去解决orz(标签-c#)
  • ¥15 VAE代码如何画混淆矩阵
  • ¥15 求遗传算法GAMS代码
  • ¥15 雄安新区高光谱数据集的下载网址打不开
  • ¥66 android运行时native和graphics内存详细信息获取
  • ¥100 求一个c#通过CH341读取数据的Demo,能够读取指定地址值的功能
  • ¥15 rk3566 Android11 USB摄像头 微信
  • ¥15 torch框架下的强化学习DQN训练奖励值浮动过低,希望指导如何调整
  • ¥35 西门子博图v16安装密钥提示CryptAcquireContext MS_DEF_PROV Error of containger opening
  • ¥15 mes系统扫码追溯功能
手机看
程序员都在用的中文IT技术交流社区

程序员都在用的中文IT技术交流社区

专业的中文 IT 技术社区,与千万技术人共成长

专业的中文 IT 技术社区,与千万技术人共成长

关注【CSDN】视频号,行业资讯、技术分享精彩不断,直播好礼送不停!

关注【CSDN】视频号,行业资讯、技术分享精彩不断,直播好礼送不停!

客服 返回
顶部