A question about register_activation hook

Question

Looking at wp codex it says:

The register_activation_hook function registers a plugin function to be run when the plugin is activated.

I am finding this to be not entirely correct, for example i can activate a plugin that adds an extra field to WP registration form (using the add extra field example in codex) which does not require the register_activation_hook function (nor the register_deactivation_hook).

What codex does not tell you is when and when not to use the register_activation_hook, now i am going to guess that the hook is only required when including files for install or creating db tables on plugin activation, i would be grateful if someone who has more knowledge of WP and the correct use of the register/deregister hooks could clarify its correct usage.

regards

Answer 1

The register_activation_hook() is actually just a wrapper for add_action('activate_' . $file, $function); and is only executed when a plugin is activated.

This action/function is meant to be used by anything that should only execute once when the plugin is activated, things which would include stuff like

• adding custom terms to taxonomies

• create new database tables or rows

• running one time db processes which might include updating certain tables, columns or rows

• flush rewrite rules

On the opposite, register_deactivation_hook() only executes when a plugin is deactivated. This hook/function/action is meant for running processes to clean up after the plugin, which may include

• restoring db tables, row or columns which was altered

• removing custom db tables which was added by the plugin

• removing any custom options which was added by the plugin that would not be necessary anymore