<?php

// If subsites is installed
if (class_exists('Users_Account_Controller')) {
    Users_Account_Controller::add_extension('OrdersUserAccountControllerExtension');
    Member::add_extension('OrdersMemberExtension');
}
// If subsites is installed
if (class_exists('Subsite')) {
    Order::add_extension('SubsitesOrdersExtension');
    OrderAdmin::add_extension('SubsiteMenuExtension');
}
// If subsites is installed
if (class_exists('SiteConfig')) {
    SiteConfig::add_extension('OrdersSiteConfigExtension');
}
<?php

// Extentions
SiteConfig::add_extension('Ext_Commerce_SiteConfig');
Image::add_extension('Ext_Commerce_Image');
Controller::add_extension('Ext_Commerce_Controller');
Group::add_extension('Ext_Commerce_Group');
Member::add_extension('Ext_Commerce_Member');
if (class_exists('Users_Account_Controller')) {
    Users_Account_Controller::add_extension('Ext_Commerce_UsersController');
}
// If subsites is installed
if (class_exists('Subsite')) {
    Product::add_extension('Ext_Subsites_CommerceObject');
    ProductCategory::add_extension('Ext_Subsites_CommerceObject');
    Order::add_extension('Ext_Subsites_CommerceObject');
    CatalogueAdmin::add_extension('SubsiteMenuExtension');
    LocaliseAdmin::add_extension('SubsiteMenuExtension');
    OrderAdmin::add_extension('SubsiteMenuExtension');
}
LeftAndMain::add_extension('Ext_Commerce_LeftAndMain');
// Setup google sitemaps
if (class_exists("GoogleSitemap")) {
    GoogleSitemap::register_dataobject('Product');
    GoogleSitemap::register_dataobject('ProductCategory');
}
<?php

if (class_exists("Users_Account_Controller")) {
    Users_Account_Controller::add_extension("CheckoutUserAccountControllerExtension");
}
<?php

if (ClassInfo::exists('Commenting')) {
    // Add commenting to discussions
    Commenting::add('Discussion', array("require_login" => true, "required_permission" => "DISCUSSIONS_REPLY", "order_comments_by" => "\"Created\" ASC"));
    Object::add_extension("Member", "DiscussionsMember");
    Object::add_extension("Group", "DiscussionsGroup");
    Object::add_extension("Comment", "DiscussionsComment");
    if (class_exists('Users_Account_Controller')) {
        Users_Account_Controller::add_extension('DiscussionsUsersController');
    }
}