Websockets & PHP

Question

I'm starting to consider websockets as a solution to replace long polling in a new build PHP app I am commissioning.

I have a few questions which I wonder if people could help me out with.

1. Can a Nodejs server call PHP and if it did wouldn't it suffer the same shortcomings as just going through Apache in terms of the connections? We all know nodejs is non blocking and Apache etc isn't but if Nodejs is just making a call to a PHP server in it's own procedure would that not bottle neck in a similar way?
2. Are PHP and websockets a good match?
3. Are there any good js libraries besides socketio which apparently only works with Nodejs?
4. Has anyone found a good tutorial which uses websockets and a PHP backend maybe using something like that Ratchet PHP library which might help me get on my way?

Thoughts would be muchly appreciated.

Answer 1

Please excuse my paraphrasing of your questions.

1: Can Node.js call PHP, and wouldn't that have the same shortcomings as Apache?

Calling a run-once PHP script will have the same general shortcomings as calling a web page, except that you are removing an extra layer of processing. Apache or any web server itself is such a thin layer that, while you'll save some time, the savings will be insignificant.

If PHP is more effective at gathering data for your clients than Node.js, for whatever reason, then it might be wise to include PHP in your application.

2: Are PHP and WebSockets a good match?

Traditional PHP scripts are normally intended to be run once per request. The vast majority of PHP developers are unfamiliar with event driven development, and PHP itself does not (yet) have support for asynchronous processing.

PHP is a fast, mature scripting language that is only getting faster, even with all of its many warts and shortcomings. (Some say that its weak typing is a shortcoming. Others say that it's a shortcoming that its typing isn't weak enough.)

That said, the minimum that any language needs in order to implement WebSockets is the ability to open up a basic TCP port and listen for requests. For PHP, it is implemented as a thin wrapper around the C sockets library, and there are additional extensions and frameworks available that can also change the feel of working in TCP sockets with PHP.

PHP's garbage collector has also matured. Memory leaks come either from gross disregard for the memory space (I'm looking at you, Zend Framework) or from intentional sabotage of the garbage collection system by developers who think they're clever or want to prove how easy it is to defeat the GC. (Spoiler: It's easy in every language, if you know the details!)

It is quite possible and very easy to set up a daemon (long running background process) in PHP. It's even possible to make it well behaved enough to gracefully restart and hand its connections off to a new version of the same script, or even the same script on the same server running different versions of PHP, though this is treading out of scope just a tiny little bit.

As for whether it's a good match, that is completely up to the developer . Are you willing, able, and happy to work with PHP to write a WebSockets server, or to use one of the existing servers? Yes? Then you're a good match for PHP and WebSockets.

3: JS Libraries for WebSockets

I honestly haven't researched them.

4: Tutorials for using PHP and Websockets

I'm personally fond of this tutorial: http://www.phpbuilder.com/articles/application-architecture/optimization/creating-real-time-applications-with-php-and-websockets.html

Although I have it on good authority that the specifics of that tutorial will soon be obsolete for that specific WebSockets server. (There will still be an actively maintained legacy branch for that server, though.)

In case of link rot:

Using the PHP-Websockets server (available on Github, will be homed soon), extend the base WebSocketServer abstract class and implement the abstract methods process() , connected() , and closed() .

There's much better information at the link above, though, so follow it as long as the link exists.

Answer 2

1. It would hit the same bottleneck if you go through apache. This can be remedied by using a different web server, such as lighthttpd or nginx . You won't even need node at all.
2. PHP does not have decent shared memory making the biggest advantages of a WebSockets irrelevent. It should be decent enough if you don't want interaction between users, but even then I would have to frown upon the usage of PHP. PHP is great for a lot of things, but real-time communication is not one of them.
3. You might want to look at https://github.com/einaros/ws .
4. PHP is not a good back-end. Anything with an execution model that isn't run-and-forget in its own sandbox, such as Node , .NET , C/C++ and Java are good matches. PHP is suited for short running executions, such as actual web sites and even web services -- but not real time connections.