Removing plugin data on deletion
As with any piece of software, it is quite possible that users might decide to remove a plugin from their WordPress installation if they no longer require the functionality that it provides, or they have found an alternative that they prefer.
When this happens, the plugin author must decide whether all of the configuration data stored in the site's database should be left in place, making it easier to re-install the plugin down the road, or to remove all of this information, leaving a clean database behind.
You should have already followed the Storing user settings using arrays recipe to have options data ready for deletion, and the resulting plugin should still be active on your development site. Alternatively, you can get the resulting code (
ch3/ch2-page-header-output/ch2-page-header-output-v3.php) from the book's GitHub page. You should rename the
ch2-page-header-output-v3.php file as