function questions_init()
{
    elgg_register_library("elgg:questions", dirname(__FILE__) . "/lib/questions.php");
    add_subtype("object", 'question', 'ElggQuestion');
    update_subtype("object", 'question', 'ElggQuestion');
    add_subtype("object", 'answer', 'ElggAnswer');
    update_subtype("object", 'answer', 'ElggAnswer');
    elgg_extend_view("css/elgg", "questions/css");
    elgg_extend_view("js/elgg", "questions/js");
    elgg_register_menu_item("site", array("name" => 'questions', "text" => elgg_echo('questions'), "href" => "/questions/all"));
    elgg_register_entity_type("object", 'questions');
    elgg_register_widget_type('questions', elgg_echo("widget:questions:title"), elgg_echo("widget:questions:description"));
    $actions_base = dirname(__FILE__) . '/actions/object/question';
    elgg_register_action("object/question/save", "{$actions_base}/save.php");
    elgg_register_action("questions/delete", "{$actions_base}/delete.php");
    $actions_base = dirname(__FILE__) . '/actions/object/answer';
    elgg_register_action("object/answer/save", "{$actions_base}/save.php");
    elgg_register_entity_url_handler('object', 'question', 'questions_url_handler');
    $plugin_dir = dirname(__FILE__);
    elgg_register_entity_url_handler('object', 'answer', 'answers_url');
    elgg_register_page_handler('questions', 'questions_page_handler');
    elgg_register_page_handler('answers', 'answers_page_handler');
    $actions_base = "{$plugin_dir}/actions/object/answer";
    elgg_register_action('object/answer/add', "{$actions_base}/save.php");
    elgg_register_action('object/answer/edit', "{$actions_base}/save.php");
    elgg_register_action('answers/delete', "{$actions_base}/delete.php");
    elgg_register_plugin_hook_handler("register", "menu:owner_block", 'questions_owner_block_menu_handler');
    elgg_register_plugin_hook_handler("register", "menu:user_hover", 'questions_user_hover_menu_handler');
    elgg_register_plugin_hook_handler("register", 'menu:entity', 'questions_entity_menu_handler');
    elgg_register_plugin_hook_handler("notify:entity:message", "object", 'questions_notify_message_handler');
    add_group_tool_option('questions', elgg_echo("questions:enable"), true);
    elgg_extend_view("groups/tool_latest", "questions/group_module");
    elgg_register_plugin_hook_handler('container_permissions_check', 'object', 'questions_container_permissions_check');
}

 /**
  * Set the correct class for the GroupMail subtype
  *
  * @param string $event  the name of the event
  * @param string $type   the type of the event
  * @param mixed  $object supplied object
  *
  * @return void
  */
 public static function setGroupMailClassHandler($event, $type, $object)
 {
     if (get_subtype_id('object', \GroupMail::SUBTYPE)) {
         update_subtype('object', \GroupMail::SUBTYPE, 'GroupMail');
     } else {
         add_subtype('object', \GroupMail::SUBTYPE, 'GroupMail');
     }
 }

 /**
  * Listen to the upgrade event to set the correct class handler
  *
  * @param string $event  the name of the event
  * @param string $type   the type of the event
  * @param null   $object supplied param
  *
  * @return void
  */
 public static function setClassHandler($event, $type, $object)
 {
     if (get_subtype_id('object', \CSVExport::SUBTYPE)) {
         update_subtype('object', \CSVExport::SUBTYPE, 'CSVExport');
     } else {
         add_subtype('object', \CSVExport::SUBTYPE, 'CSVExport');
     }
 }

/**
* This function adds a class handler to object->faq
* Since the old FAQ didn't had a class
*
* @return bool
*/
function user_support_faq_class_update()
{
    $class = get_subtype_class("object", UserSupportFAQ::SUBTYPE);
    if ($class != "UserSupportFAQ") {
        return update_subtype("object", UserSupportFAQ::SUBTYPE, "UserSupportFAQ");
    }
    return true;
}

 /**
  * Update the class for publication subtype
  *
  * @param string $event  the name of the event
  * @param string $type   the type of the event
  * @param mixed  $object supplied params
  *
  * @return void
  */
 public static function setClassHandler($event, $type, $object)
 {
     // set correct class handler for Publication
     if (get_subtype_id('object', \Publication::SUBTYPE)) {
         update_subtype('object', \Publication::SUBTYPE, 'Publication');
     } else {
         add_subtype('object', \Publication::SUBTYPE, 'Publication');
     }
 }

 public static function fixClasses($event, $type, $object)
 {
     $classes = ['\\ColdTrick\\EventManager\\Event\\Day', '\\ColdTrick\\EventManager\\Event\\Slot'];
     foreach ($classes as $class) {
         if (get_subtype_class('object', $class::SUBTYPE) !== $class) {
             update_subtype('object', $class::SUBTYPE, $class);
         }
     }
 }

 /**
  * Make sure the class handler for QuickLink is correct
  *
  * @param string $event  the name of the event
  * @param string $type   the type of the event
  * @param mixed  $object misc params
  *
  * @return void
  */
 public static function setClassHandler($event, $type, $object)
 {
     // set correct class handler for QuickLink
     if (get_subtype_id('object', \QuickLink::SUBTYPE)) {
         update_subtype('object', \QuickLink::SUBTYPE, 'QuickLink');
     } else {
         add_subtype('object', \QuickLink::SUBTYPE, 'QuickLink');
     }
 }

/**
 * Performs class upgrade before init as classes are needed during init
 *
 * @return void
 */
function profile_manager_plugins_boot()
{
    $classes = ['\\ColdTrick\\ProfileManager\\CustomProfileField', '\\ColdTrick\\ProfileManager\\CustomGroupField', '\\ColdTrick\\ProfileManager\\CustomProfileType', '\\ColdTrick\\ProfileManager\\CustomFieldCategory'];
    foreach ($classes as $class) {
        $current_class = get_subtype_class('object', $class::SUBTYPE);
        if ($current_class !== $class) {
            update_subtype('object', $class::SUBTYPE, $class);
        }
    }
}

function upgrade_1395096061()
{
    $subtypes = array(HYPEGAMEMECHANICS_BADGE_SUBTYPE, HYPEGAMEMECHANICS_BADGERULE_SUBTYPE, HYPEGAMEMECHANICS_SCORE_SUBTYPE);
    foreach ($subtypes as $subtype) {
        if (get_subtype_id('object', $subtype)) {
            update_subtype('object', $subtype);
        } else {
            add_subtype('object', $subtype);
        }
    }
}

/**
 * Listen to the upgrade event
 *
 * @param string $event  the name of the event
 * @param string $type   the type of the event
 * @param mixed  $object supplied params
 */
function haarlem_tangram_upgrade($event, $type, $object)
{
    // register correct class for future use
    if (get_subtype_id('object', TangramVacancy::SUBTYPE)) {
        update_subtype('object', TangramVacancy::SUBTYPE, 'TangramVacancy');
    } else {
        add_subtype('object', TangramVacancy::SUBTYPE, 'TangramVacancy');
    }
    // reset xml cache
    haarlem_tangram_clear_cached_xml();
}

/**
 * Listen to upgrade event
 *
 * @param string $event  the name of the event
 * @param string $type   the type of the event
 * @param mixed  $object supplied params
 *
 * @return void
 */
function wizard_upgrade_system_handler($event, $type, $object)
{
    $id = get_subtype_id('object', Wizard::SUBTYPE);
    if (empty($id)) {
        // add subtype registration
        add_subtype('object', Wizard::SUBTYPE, 'Wizard');
    } elseif (get_subtype_class_from_id($id) !== 'Wizard') {
        // update subtype registration
        update_subtype('object', Wizard::SUBTYPE, 'Wizard');
    }
}

 /**
  * Check the class assosiation
  *
  * @param string $event  the name of the event
  * @param string $type   the type of the event
  * @param mixed  $object supplied params
  *
  * @return void
  */
 public static function checkClasses($event, $type, $object)
 {
     if (get_subtype_id('object', \APIApplication::SUBTYPE)) {
         update_subtype('object', \APIApplication::SUBTYPE, 'APIApplication');
     } else {
         add_subtype('object', \APIApplication::SUBTYPE, 'APIApplication');
     }
     if (get_subtype_id('object', \APIApplicationUserSetting::SUBTYPE)) {
         update_subtype('object', \APIApplicationUserSetting::SUBTYPE, 'APIApplicationUserSetting');
     } else {
         add_subtype('object', \APIApplicationUserSetting::SUBTYPE, 'APIApplicationUserSetting');
     }
 }

function widget_manager_init()
{
    // check valid WidgetManagerWidget class
    if (get_subtype_class("object", "widget") == "ElggWidget") {
        update_subtype("object", "widget", "WidgetManagerWidget");
    }
    elgg_trigger_event("widgets_init", "widget_manager");
    if (elgg_is_active_plugin("groups") && elgg_get_plugin_setting("group_enable", "widget_manager") == "yes") {
        // add the widget manager tool option
        $group_option_enabled = false;
        if (elgg_get_plugin_setting("group_option_default_enabled", "widget_manager") == "yes") {
            $group_option_enabled = true;
        }
        if (elgg_get_plugin_setting("group_option_admin_only", "widget_manager") != "yes") {
            // add the tool option for group admins
            add_group_tool_option('widget_manager', elgg_echo('widget_manager:groups:enable_widget_manager'), $group_option_enabled);
        } elseif (elgg_is_admin_logged_in()) {
            add_group_tool_option('widget_manager', elgg_echo('widget_manager:groups:enable_widget_manager'), $group_option_enabled);
        } elseif ($group_option_enabled) {
            // register event to make sure newly created groups have the group option enabled
            elgg_register_event_handler("create", "group", "widget_manager_create_group_event_handler");
            elgg_register_plugin_hook_handler('get_list', 'default_widgets', 'widget_manager_group_widgets_default_list');
        }
    }
    // extend CSS
    elgg_extend_view("css/elgg", "widget_manager/css/global");
    elgg_extend_view("css/admin", "widget_manager/css/global");
    elgg_extend_view("js/elgg", "widget_manager/js/site");
    elgg_extend_view("js/admin", "widget_manager/js/admin");
    // register a widget title url handler
    elgg_register_entity_url_handler("object", "widget", "widget_manager_widget_url_handler");
    // multi dashboard support
    add_subtype("object", MultiDashboard::SUBTYPE, "MultiDashboard");
    if (elgg_is_logged_in() && widget_manager_multi_dashboard_enabled()) {
        elgg_register_page_handler("multi_dashboard", "widget_manager_multi_dashboard_page_handler");
        $options = array("type" => "object", "subtype" => MultiDashboard::SUBTYPE, "owner_guid" => elgg_get_logged_in_user_guid(), "count" => true);
        $tab_count = elgg_get_entities($options);
        if ($tab_count < MULTI_DASHBOARD_MAX_TABS) {
            elgg_register_menu_item("extras", array("name" => "multi_dashboard", "text" => elgg_view_icon("home"), "href" => "multi_dashboard/edit/?internal_url=" . urlencode(current_page_url()), "title" => elgg_echo("widget_manager:multi_dashboard:extras"), "rel" => "nofollow", "id" => "widget-manager-multi_dashboard-extras"));
        }
        elgg_extend_view("page/elements/sidebar", "widget_manager/multi_dashboard/sidebar", 400);
        elgg_register_event_handler("create", "object", "widget_manager_create_object_handler");
        elgg_register_plugin_hook_handler("route", "dashboard", "widget_manager_dashboard_route_handler");
        elgg_register_plugin_hook_handler("action", "widgets/add", "widget_manager_widgets_add_action_handler");
        elgg_register_action("multi_dashboard/edit", dirname(__FILE__) . "/actions/multi_dashboard/edit.php");
        elgg_register_action("multi_dashboard/delete", dirname(__FILE__) . "/actions/multi_dashboard/delete.php");
        elgg_register_action("multi_dashboard/drop", dirname(__FILE__) . "/actions/multi_dashboard/drop.php");
        elgg_register_action("multi_dashboard/reorder", dirname(__FILE__) . "/actions/multi_dashboard/reorder.php");
    }
}

function hj_forum_1358206168()
{
    $subtypes = array('hjforum' => 'hjForum', 'hjforumcategory' => 'hjForumCategory', 'hjforumtopic' => 'hjForumTopic', 'hjforumpost' => 'hjForumPost');
    foreach ($subtypes as $subtype => $class) {
        if (get_subtype_id('object', $subtype)) {
            update_subtype('object', $subtype, $class);
        } else {
            add_subtype('object', $subtype, $class);
        }
    }
    $subtypeIdForum = get_subtype_id('object', 'hjforum');
    $subtypeIdForumTopic = get_subtype_id('object', 'hjforumtopic');
    $subtypeIdAnnotation = get_subtype_id('object', 'hjannotation');
    $dbprefix = elgg_get_config('dbprefix');
    $segments = elgg_get_entities_from_metadata(array('types' => 'object', 'subtypes' => 'hjsegment', 'metadata_name_value_pairs' => array('name' => 'handler', 'value' => 'hjforumtopic'), 'limit' => 0));
    /**
     * Upgrade :
     * 1. Convert segmented hjForumTopic objects to hjForum objects
     * 2. Remove segments
     * 3. Convert widgets to categories
     */
    foreach ($segments as $segment) {
        $forum = get_entity($segment->container_guid);
        $query = "UPDATE {$dbprefix}entities SET subtype = {$subtypeIdForum} WHERE subtype = {$subtypeIdForumTopic} AND guid = {$forum->guid}";
        update_data($query);
        $widgets = elgg_get_entities(array('types' => 'object', 'subtypes' => 'widget', 'container_guids' => array($segment->guid, $forum->guid), 'limit' => 0));
        if ($widgets) {
            $forum->enable_subcategories = true;
            foreach ($widgets as $widget) {
                $threads = elgg_get_entities_from_metadata(array('types' => 'object', 'subtypes' => 'hjforumtopic', 'metadata_name_value_pairs' => array(array('name' => 'widget', 'value' => $widget->guid)), 'limit' => 0));
                $cat = new ElggObject();
                $cat->subtype = 'hjforumcategory';
                $cat->owner_guid = elgg_get_logged_in_user_guid();
                $cat->container_guid = $forum->guid;
                $cat->title = $widget->title;
                $cat->description = '';
                $cat->access_id = ACCESS_PUBLIC;
                $cat->save();
                foreach ($threads as $thread) {
                    $query = "UPDATE {$dbprefix}entities SET container_guid = {$forum->guid} WHERE guid = {$thread->guid}";
                    update_data($query);
                    unset($thread->widget);
                    $thread->setCategory($cat->guid, true);
                }
                $widget->disable('plugin_version_upgrade');
            }
        }
        $segment->disable('plugin_version_upgrade');
    }
}

/**
 * Do something on the 'upgrade', 'system' event (when running upgrade.php)
 *
 * @param string $event  which event was triggered
 * @param string $type   what is the type of the event
 * @param mixed  $object On what object was the event triggered
 *
 * @return void
 *
 * @see elgg_trigger_event()
 */
function newsletter_upgrade_event_handler($event, $type, $object)
{
    // amke sure the correct classes are set for our own classes
    if (!update_subtype("object", Newsletter::SUBTYPE, "Newsletter")) {
        // first time the plugin was activated
        add_subtype("object", Newsletter::SUBTYPE, "Newsletter");
    }
    if (!update_subtype("object", NewsletterSubscription::SUBTYPE, "NewsletterSubscription")) {
        // first time the plugin was activated
        add_subtype("object", NewsletterSubscription::SUBTYPE, "NewsletterSubscription");
    }
    // proccess upgrade scripts
    $upgrade_scripts = array();
    $upgrade_dir = dirname(__FILE__) . "/upgrades/";
    $fh = opendir($upgrade_dir);
    // read all available upgrade scripts
    if (!empty($fh)) {
        while (($upgrade_file = readdir($fh)) !== false) {
            if (!is_dir($upgrade_dir . $upgrade_file)) {
                $upgrade_scripts[] = $upgrade_file;
            }
        }
        closedir($fh);
    }
    if (!empty($upgrade_scripts)) {
        // get already run scripts
        $upgrades = datalist_get("processed_upgrades");
        $processed_upgrades = unserialize($upgrades);
        if (!is_array($processed_upgrades)) {
            $processed_upgrades = array();
        }
        // do we have something left
        $unprocessed = array_diff($upgrade_scripts, $processed_upgrades);
        if (!empty($unprocessed)) {
            // proccess all upgrades
            foreach ($unprocessed as $script) {
                include $upgrade_dir . $script;
                $processed_upgrades[] = $script;
            }
            // save new list
            elgg_set_processed_upgrades($processed_upgrades);
        }
    }
}

 /**
  * Listen to upgrade event
  *
  * @param string $event  the name of the event
  * @param string $type   the type of the event
  * @param mixed  $object supplied params
  *
  * @return void
  */
 public static function fixClasses($event, $type, $object)
 {
     $id = get_subtype_id('object', \Wizard::SUBTYPE);
     if (empty($id)) {
         // add subtype registration
         add_subtype('object', \Wizard::SUBTYPE, 'Wizard');
     } elseif (get_subtype_class_from_id($id) !== 'Wizard') {
         // update subtype registration
         update_subtype('object', \Wizard::SUBTYPE, 'Wizard');
     }
     $id = get_subtype_id('object', \WizardStep::SUBTYPE);
     if (empty($id)) {
         // add subtype registration
         add_subtype('object', \WizardStep::SUBTYPE, 'WizardStep');
     } elseif (get_subtype_class_from_id($id) !== 'WizardStep') {
         // update subtype registration
         update_subtype('object', \WizardStep::SUBTYPE, 'WizardStep');
     }
 }

/**
 * The Wire initialization
 */
function thewire_init()
{
    global $CONFIG;
    // this can be removed in favor of activate/deactivate scripts
    if (!update_subtype('object', 'thewire', 'ElggWire')) {
        add_subtype('object', 'thewire', 'ElggWire');
    }
    // register the wire's JavaScript
    $thewire_js = elgg_get_simplecache_url('js', 'thewire');
    elgg_register_simplecache_view('js/thewire');
    elgg_register_js('elgg.thewire', $thewire_js, 'footer');
    elgg_register_ajax_view('thewire/previous');
    // add a site navigation item
    $item = new ElggMenuItem('thewire', elgg_echo('thewire'), 'thewire/all');
    elgg_register_menu_item('site', $item);
    // owner block menu
    elgg_register_plugin_hook_handler('register', 'menu:owner_block', 'thewire_owner_block_menu');
    // remove edit and access and add thread, reply, view previous
    elgg_register_plugin_hook_handler('register', 'menu:entity', 'thewire_setup_entity_menu_items');
    // Extend system CSS with our own styles, which are defined in the thewire/css view
    elgg_extend_view('css', 'thewire/css');
    //extend views
    elgg_extend_view('activity/thewire', 'thewire/activity_view');
    elgg_extend_view('profile/status', 'thewire/profile_status');
    elgg_extend_view('js/initialise_elgg', 'thewire/js/textcounter');
    // Register a page handler, so we can have nice URLs
    elgg_register_page_handler('thewire', 'thewire_page_handler');
    // Register a URL handler for thewire posts
    elgg_register_entity_url_handler('object', 'thewire', 'thewire_url');
    elgg_register_widget_type('thewire', elgg_echo('thewire'), elgg_echo("thewire:widget:desc"));
    // Register for search
    elgg_register_entity_type('object', 'thewire');
    // Register granular notification for this type
    register_notification_object('object', 'thewire', elgg_echo('thewire:notify:subject'));
    // Listen to notification events and supply a more useful message
    elgg_register_plugin_hook_handler('notify:entity:message', 'object', 'thewire_notify_message');
    // Register actions
    $action_base = $CONFIG->pluginspath . 'thewire/actions';
    elgg_register_action("thewire/add", "{$action_base}/add.php");
    elgg_register_action("thewire/delete", "{$action_base}/delete.php");
    elgg_register_plugin_hook_handler('unit_test', 'system', 'thewire_test');
}

<?php

/** @todo: remove hjForm & hjField */
$subtypes = array('hjform' => 'hjForm', 'hjfield' => 'hjField', 'hjfile' => 'hjFile', 'hjfilefolder' => 'hjFileFolder', 'hjsegment' => 'hjSegment', 'hjannotation' => 'hjAnnotation', 'hjcategory' => 'hjCategory');
foreach ($subtypes as $subtype => $class) {
    if (get_subtype_id('object', $subtype)) {
        update_subtype('object', $subtype, $class);
    } else {
        add_subtype('object', $subtype, $class);
    }
}

<?php

/**
 * Elgg 1.9.0-dev upgrade 2013010400
 * comments_to_entities
 *
 * Convert comment annotations to entities.
 *
 * Register comment subtype and add ElggUpgrade for ajax upgrade.
 * 
 * We do not migrate comments in this upgrade. See the comment
 * upgrade action in actions/admin/upgrades/upgrade_comments.php for that.
 */
// Register subtype and class for comments
if (get_subtype_id('object', 'comment')) {
    update_subtype('object', 'comment', 'ElggComment');
} else {
    add_subtype('object', 'comment', 'ElggComment');
}
$access_status = access_get_show_hidden_status();
access_show_hidden_entities(true);
$ia = elgg_set_ignore_access(true);
// add ElggUpgrade object if need to migrate comments
$options = array('annotation_names' => 'generic_comment', 'order_by' => 'n_table.id DESC', 'count' => true);
if (elgg_get_annotations($options)) {
    $url = "admin/upgrades/comments";
    $upgrade = new ElggUpgrade();
    // Create the upgrade if one with the same URL doesn't already exist
    if (!$upgrade->getUpgradeFromURL($url)) {
        $upgrade->setURL($url);
        $upgrade->title = 'Comments Upgrade';

<?php

/**
 * This script is run when the plugin gets deactivated
 */
// undo class handlers for subtype
update_subtype('object', GroupMail::SUBTYPE);