Keeping a live connection with php?

Question

I am working on a project has me constantly pinging a php script for new data, so if I understand this correctly that means that the php script being pinged gets run over and over indefinitely. It works but i'm guessing its a huge strain on the server, and is probably considered ugly and bad practice. Am I right about that?

Is there any way I could keep the connection to the script alive and make use of php's built in output buffering to flush the contents I need, but keep the script running for infinity using some sort of loop so when new data is available it can be output. Is this a bad idea as well?

I'm just looking for input form developers out there with more experience.

One last thing...

Are there any other ways to keep a constant flow of data going (excluding technologies such as flash or silverlight)?

Answer 1

If what you have currently works and continues to work when tested against the kind of load you might expect in this application, it is not really considered bad practice. It is not a crime to keep it simple if it works. Anything that does what you are describing is going to go against the grain of the original model of the web, so you're venturing into shaky territory.

I do recommend you check out the Comet technique. It is mostly popular for the inverse of what you want - the server pushing information to a page continuously - but it can obviously work both ways. Although your mileage may vary, I've heard good things. As Wikipedia describes it:

In web development, Comet is a neologism to describe a web application model in which a long-held HTTP request allows a web server to push data to a browser, without the browser explicitly requesting it. Comet is an umbrella term for multiple techniques for achieving this interaction. All these methods rely on features included by default in browsers, such as Javascript, rather than on non-default plugins.

Answer 2

It almost seems like php wouldn't be the best choice of language for this. Possibly consider something like scala or erlang which are setup to handle this type of long lived messaging better.

Answer 3

You have to learn how to use sockets in php.

Start from here: http://php.net/manual/en/book.sockets.php

And afair here is useful manual about writing standalone php apps: Advanced PHP Programming

Answer 4

I'd say that depends. If you want the data transfers to be started by the client, your best choice here would be some ajax (like getxmlhttpobject or just iframes if you feel like cheating :P). If you want the transfers to be started by the server, then, perhaps php is not the language you want to use.

Answer 5

You can use ajax to have http-streaming. Take a look at ajaxpatterns.