Does PHP support asynchronous programming?

Question

I'm new to PHP. I am familiar with ASP.NET which support asynchronous programming. That is, if one request needs to do some I/O job. It is suggested to program the web page with BeginProcess/EndProcess way. The asynchronous programming is key to improve scalability.

I'm wondering whether there is counterpart of asynchronous programming(BeginXXXX/EndXXXX) in PHP world.

Answer 1

In .NET BeginXXX/EndXXX paradigm relies heavily on threading, while on PHP I am not sure that you could even start a new thread (except maybe the PECL package).

FastCGI is the alternative to multithreading in most interpreted languages. Instead of spawning new threads it uses processes, but as spawning a new process is expensive, it keeps a reusable process pool just as the ThreadPool in .NET.

Answer 2

The core has a set of process control functions, including the ability to fork a process. I don't know that I'd use these in a web script, but have used them in command line scripts before.

http://www.php.net/manual/en/book.pcntl.php

http://www.php.net/manual/en/pcntl.example.php

Answer 3

If the I/O is performed with sockets or files you should use stream_socket_select() or stream_select() respectively (similar to system calls in C/C++).

Here's a simple command line chat tutorial done with PHP: Simple PHP socket-based terminal chat

Note: This is not a general multi-threading solution, but a simple solution for situations where you need "semi-parallel" I/O

Answer 4

Here's an interesting link on the subject of PHP multiplexing with PHP4 and PHP5 samples:

http://netevil.org/blog/2005/may/guru-multiplexing

Answer 5

PHP doesn't, but you could use AJAX once the page has loaded, which will allow asynchronous requests.

Honestly though, there is no point. If you really want that heavyweight of a back end, you're better off writing a separate program that does the heavy lifting. PHP modules are written in pure C as far as I'm aware, so you should be able to use that and then call your own custom function from PHP.