We are creating a php script project; which we will be selling to customers.
The customers can host the script on their web server.

We would like to develop an update or upgrade process for this script.
Means if a customer is using the version 1.2 of the script and we have released the new version 1.3 of the script, the users will be able to see a text saying "new version is available" in the backend control panel.

The user can than go to update or upgrade page and hit a button to auto update the script.
I can understand that this process will involve the following things: 1. A process to check the current version of the script available from our home website.
2. File update process: download and update the required files from my server on the client server.
3. Make required database changes: Download the upgrade sql file from my home server and run it against the database.

I tried google to find a good start up tutorial to give me a kick start and to verify if I am missing something but I am not able to find anything.
Can you point me to some kick start tutorials or guide about developing or managing update process of a script?
I know that all major open source scripts like Wordpress, Joomla, osCommerce, Magento have this facility. So there must be resources available for this on the internet.

Bizim zaman için teşekkür ederiz .. eğlenin! :)