uninstall.php

<?php
/**
 * Fired when the plugin is uninstalled.
 *
 * Removes plugin options and per-post metadata so no orphaned data is
 * left behind. Runs for every site on multisite installs.
 *
 * @since   2.0.0
 * @package Auto_Refresh_Post_Page
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

if ( ! defined( 'WP_UNINSTALL_PLUGIN' ) ) {
	exit;
}

/**
 * Delete all plugin data for the current site.
 *
 * @return void
 */
function arpp_uninstall_site() {
	delete_option( 'ARPP_settings' );
	delete_option( 'ARPP_my_option_name' );
	delete_option( 'ARPP_version' );

	delete_post_meta_by_key( '_arpp_post_settings' );
	delete_post_meta_by_key( 'ARPP_duration_options' );
}

if ( is_multisite() ) {
	$arpp_site_ids = get_sites( array( 'fields' => 'ids' ) );
	foreach ( $arpp_site_ids as $arpp_site_id ) {
		switch_to_blog( $arpp_site_id );
		arpp_uninstall_site();
		restore_current_blog();
	}
} else {
	arpp_uninstall_site();
}