Tipos about which CMS use

Hi there, I'd like to replace my 'intranet' site with a CMS system to speed up the edit process. Some of my requirements are : - written in PHP :) - mysql based - documented/'well structured' - to allow development of customizations - ability to define which pages or sections are public and which are private (and in this case which users can access) - use AJAX (not mandatory) but since some access to the page will come from dial-up to reduce the need to transfer entire html just to update a search or list contents.. thanks