How websocket works in php

Question

I have this doubt, for example, I have a server written in PHP.

When a user A connects to this server the server performs an action that takes 4 seconds for example, if before that deadline a new user B connect, it will have to wait for user execution A finish before making your run? or how it works? I’m lost.

I don’t know if I made myself clear..

Answer 1

Websocket

In websockets the process is quite similar to normal HTTP, but the difference is that we do not close the connection and we do not need to order the server again to know when there is something new, the event inside ws receives signals or data directly from the server.

If you write a websocket basic probably it will be synchronous if the user A send something very long probably the process will be "stopped" until finished, but at the time of sending to other users the long message of the user A all will receive at the same time probably.

However when reading about the ratchetphp/Ratchet, more specifically to this message:

• https://github.com/ratchetphp/Ratchet/issues/214#issuecomment-49737414

  He claims that the Ratchet is asynchronous and indicates two links. If you look at the repository https://github.com/reactphp/socket will see the following description:

  Asynchronous socket server (en: Asynchronous server socket)

Also on the link indicated in the github comment, there is the option to use "child process":

• https://github.com/reactphp/child-process)

  And there in the repository is the following description:

  Asynchronous Childprocess (en: Process asynchronous children)

  Example of use:

  $loop = React\EventLoop\Factory::create();
  
  $process = new React\ChildProcess\Process('echo foo');
  
  $process->on('exit', function($exitCode, $termSignal) {
      // ...
  });
  
  $loop->addTimer(0.001, function($timer) use ($process) {
      $process->start($timer->getLoop());
  
      $process->stdout->on('data', function($output) {
          // ...
      });
  });
  
  $loop->run();
  

In short: So how the websockets work in PHP will depend on how the code was written, the reactphp is already asynchronous and still supports child-process, then using well the library, the user B will not need to wait for the user A to interact with the websocket.

A socket within php works much like a normal socket, we usually use the fsockopen or stream, or even other libraries such as curl.

PHP is written in C++, so it probably depends on which php extension you refer to. But the basic thing is it connects by a socket, it will depend on you as a developer set, for example to make an HTTP request it is necessary to make a request by TCP.

---

HTTP servers

But if what you want to understand is how it works to manage client requests to a "normal" server that uses PHP (served production), I must tell you that it is not php that manages this, but rather the Apache or Nginx or lighttpd, which are HTTP servers.

• Note that PHP is the back-end of the HTTP server, as well as instead of PHP, you can use Python or other interpreters/compilers, so PHP responds to the HTTP server and this same server responds to the client (user’s browser).

Both Apache and other servers share requests by childs (which are a kind of "thread"), in apache the process is synchronous but still has several Children which allows several people to access without needing one to wait for the other. You can set limits on Apache itself, remember the higher the limit the more memory will be needed.

On the other hand, Ngnix and lighttpd servers claim to be asynchronous, which probably divides the childs and allows a greater number of users to access at the same time, but it is still used these childs.

Childs are like threads or subprocesses, the connections are probably divided between these subprocesses and returned later.

Each server type has its own way of managing connections and replying requests, this can also vary with the server type, such as a server that uses the Linux kernel or a Windows-based server.

But in the basic user B no need to wait for the A finish his execution.