register_uninstall_hook called twice on each page

[tristanleboss]

Hello,

The wordpress function register_uninstall_hook is called twice on each page. Indeed, it is executed in:

• add_hook function from class CPTP_Module_Option from file ./CPTP/Module/Option.php
• add_hook function from class CPTP_Module_FlushRules from file ./CPTP/Module/FlushRules.php

This function should only be called once from the function you define as an activation hook using register_activation_hook. Have a look at the note at the bottom of this page: https://developer.wordpress.org/reference/functions/register_uninstall_hook/

Indeed, this WordPress function stores your uninstall function in an uninstall_plugins option stored in wp_options table. So no need to call it on each page. Calling it at plugin activation is enough.

Indeed, it actually executes 2 UPDATE queries on each page of my site. It's a problem if you use a caching plugin (like W3 Total Cache) because when an UPDATE query is done on a table, the caching plugin needs to discard the cached queries who use this table. So, on each page, my cache clears the cache for the wp_options table killing any caching effect.

Regards,

Tristan

[tristanleboss]

Actually, I also discovered that calling this function twice doesn't do what I think you expect: uninstall hooks are not combined. Indeed, the last one replace the previous one.

Here are the 2 queries executed by the register_uninstall_hook function (which internally uses update_option). We can clearly see that it replaces the previously defined uninstall hook.

UPDATE wp_options
SET option_value = 'a:1:{s:59:"custom-post-type-permalinks/custom-post-type-permalinks.php";a:2:{i:0;s:18:"CPTP_Module_Option";i:1;s:14:"uninstall_hook";}}' WHERE option_name = 'uninstall_plugins'

UPDATE wp_options
SET option_value = 'a:1:{s:59:"custom-post-type-permalinks/custom-post-type-permalinks.php";a:2:{i:0;s:22:"CPTP_Module_FlushRules";i:1;s:14:"uninstall_hook";}}' WHERE option_name = 'uninstall_plugins'