在CodeIgniter中的不同项目之间共享控制器，模型和视图

Kohana, due to cascading file system and modules, allows to share code in common projects, that contains controllers, views and models directories. How can I do it in codeigniter? I want to create sites, that will share some code (admin area views, some models). That is easy in Kohana, we just have to add another directory for Kohana::find_file().Kohana, due to cascading file system and module