On of the most annoying things I find about WordPress Plugins is that once you decide you no longer want to use one, simply deactivating the plugin, in most cases, still leaves behind a bunch of garbage in your database. Maybe you like to test a plugin to see what it does or maybe it sounded great but in reality it wasn’t quite what you were after. So you deactivate it and/or delete it thinking it’s gone right? Usually not. You might be left with altered database tables, indexes which now make your database inefficient, various settings and options that are now orphaned.

I recently decided I didn’t want to be part of this crowd. I wanted to give a reasonable option to my plugin users to 100% completely uninstall a plugin if they so chose. After a little research and some tweaking here’s what I came up with. It’s really rather simple.

There are 3 parts.
1. The uninstall form
2. The check for the uninstall submission
3. The uninstall itself

So here we go. First you need to create an uninstall form in your plugin. As you can see in the picture, I include a check box the user must check to confirm they want to uninstall the plugin. The form should look something like:

<form method="post">
<input id="plugin" name="plugin" type="hidden" value="plugin/plugin.php" />

	if ( isset( $_POST['uninstall'] ) && ! isset( $_POST['uninstall_confirm'] ) ) {

You must check the confirm box before continuing.

	}

The options for this plugin are not removed on deactivation to ensure that no data is lost unintentionally.

If you wish to remove all plugin information for your database be sure to run this uninstall utility first.

<input name="uninstall_confirm" type="checkbox" value="1" />Please confirm before proceeding

<input class="button-secondary" name="uninstall" type="submit" value="Uninstall" />
</form>

I like to wrap this in a function called pluginname_form_uninstall() to prevent conflicts then add that to the plugin options screen. Next we need to check to see if the form was submitted.

if ( isset( $_POST['uninstall'], $_POST['uninstall_confirm'] ) ) {
	pluginname_uninstall();
}

Somewhere near the top of the plugin or before execution starts add a check of the $_POST vars to see if our uninstall option was submitted. If it was we call the third piece of this puzzle, the uninstall function itself.

function pluginname_uninstall() {

	delete_option( 'plugin_version' );
	delete_option( 'plugin_options' );

        // This is where you would remove and tables, indexes or fields you added when your plugin was first activated. Also anything else that caused modification to the database should be undone here.

        // Do not change (this deactivates the plugin)
	$current = get_settings('active_plugins');
	array_splice($current, array_search( $_POST['plugin'], $current), 1 ); // Array-function!
	update_option('active_plugins', $current);
	header('Location: plugins.php?deactivate=true');
}

This is pretty simple but it depends on what you’ve added to the database.

• First use the delete_option function to remove any settings added to the wp_options table.
• Next undo any SQL modification you made when your plugin was created. Any tables, fields or indexes added need to be removed or changed like your plugin was never there.
• The final part deactivates the plugin and switches the user to the plugins management screen.

At this point the plugin can be activated again or deleted.

As you can this this really is fairly simple, I’m not why more developers don’t use something similar to this. I for one can’t stand to have a cluttered up database of things I don’t need.