Question

In the Joomla back-end, the administrator would do modifications using the GUI.
Say a module is enabled(just click the check box).
What happens in php-level?(what happens to the code?)
Some trivial assumptions I come up with are,
-commenting/uncommenting
-some code snippets are added/removed
-configuration(ex: xml) files are modified/created

Answer 1

Joomla itself doesn’t really modify files on disk much at all. The only exceptions I can think of are:

• Installing an extension (writes to ‘/tmp’, and then the final location for the extension files)
• Saving global configuration options (writes to ‘/configuration.php’)
• Caching (writes to ‘/cache’)

All other configuration changes, entered data, etc from the admin area (and frontend) are stored in the Joomla database.

So the example given (enabling/disabling a module) doesn’t edit or create any files. It only makes changes in a core database table (jos_modules, if your DB prefix is ‘jos_’). Module inclusion on all pages is dynamically evaluated per page-load based on the code in your template, as @Hanny mentions.