So, this script is also compatible with Word Press websites as well.

The user either runs this in place or downloads and runs it.

This wraps your exe in the code that will check the web location (at a frequency of your choosing) for updates. You don't have to make any special changes to your code to enable this. Just modify and extend your code as normal, compile, build, package and upload.

Of course you can have many variation, but this is the basic way to do it.

On Windows, at least, some software install an updater deamon that is always on and checks for new updates of the software it takes care (Google Updater, for example).

Visual Studio provides full support for publishing and updating applications deployed with Click Once technology if you have developed your projects with Visual Basic and Visual C#.

This creates a downloadable setup exe which you load up to the web.

Say I worked on a new feature on the software and I want it to be available for people who already have the older version, how can I make the software find my new version, patch it, and then go about it's business. Is there something special in my code I should have to allow updating?

EDIT: I'm sorry for the confusion, but I was meaning a more code-wise answer.

Further, you can also hide the skip button so the user can’t proceed without updating the service.

On the other hand, you can allow the user to run an older version for a limited time.

Then, this auto update PHP script is the best solution for you.