PHP - AJAX jQuery Server “Push” System

Question

I am creating a web app that requires a live notification system. How would I set up my server to pull data from a mySQL database and then push it to the browser. I have absolutely NO idea how to do this. If anybody can help, it would be much appreciated! Thank you so much!

EDIT: I should probably be more specific, I am pulling data as in XYZ recently created an account, XZY recently ... Thanks so much!

Answer 1

You cannot push data to a browser, but what you can do is set up your webpage to poll your server every few seconds for updates. An example setup would be:

From within your website, have a javascript function that runs on a timer every few seconds (or whatever interval works best for your situation).

Start that timer on page load.

That javascript function invokes an AJAX call to a web service on your web server (more on that in a second).

On the server side you'll need some sort of system that tracks these events and stores them somewhere such as in a database table with a timestamp. So for example when XYZ creates an account, that would be logged in this "event" table in the db.

The web service called by the AJAX call will then run a query on that table and retrieve all entries since the last time it was called. Then just update the webpage with those results.

It's obviously not 100% "live" as there will be a small delay depending on what time interval you set in the JS timer but it's pretty close.

Answer 2

You can create a push notification service for your website utilizing websockets and graceful degradation to a long polling fallback for browsers that don't support websockets. This does require a healthy amount of technical/programming knowledge.

Some good resources for this are: http://socket.io (which uses a node.js backend for the web sockets and handles degradation) http://pusherapp.com (a commercial solution if you don't want to roll and maintain your own service)

For a list of browsers that support websockets, you can search for "caniuse" -- which provides great details to features supported by browser versions

Note: For multi-million user applications like Facebook, I would assume they've weighed the advantages of running websockets for 50+ million simultaneous users and concluded that keeping data consistent across all the nodes connected to the millions of sockets would be too much. I can imagine it would be a logic nightmare to do that on a socket system instead of a basic action sql-like infrastructure. I can't speak on their behalf though, this is simply my assumption. However, you'd be surprised how many sites have been using push and polling systems lately :)