footnotes/includes/uninstall.php

<?php
/**
 * Created by Stefan Herndler.
 * User: Stefan
 * Date: 15.05.14
 * Time: 16:21
 * Version: 1.0.6
 * Since: 1.0
 */

/* check if the wordpress function to uninstall plugins is active */
if (!defined('WP_UNINSTALL_PLUGIN')) {
    header('Status: 403 Forbidden');
    header('HTTP/1.1 403 Forbidden');
    exit();
}

/*
 * requires the defines of the plugin
 * @since 1.0.6
 */
require_once(dirname(__FILE__) . '/defines.php');

/* uninstalling the plugin is only allowed for logged in users */
if (!is_user_logged_in()) {
    wp_die(__('You must be logged in to run this script.', FOOTNOTES_PLUGIN_NAME));
}

/* current user needs the permission to (un)install plugins */
if (!current_user_can('install_plugins')) {
    wp_die(__('You do not have permission to run this script.', FOOTNOTES_PLUGIN_NAME));
}

/*
 * delete the settings container in the database
 * @since 1.0.6
 */
delete_option(FOOTNOTE_SETTINGS_CONTAINER);