Custom CMS with php and mysql

I need a custom CMS system for a new project I have lined up. It must use php and mysql. I would like the admin area to have the ability to create users who can edit pages and have levels of usability. By that I mean there must be one master site admin, senior editors and plain editors. The master admin must be able to set editing rights for the users. By that I mean senior editors will be able to create new pages and edit existing pages, whereas plain editors will only be able to edit pages. I would like the option for all changes not to be active until verified by the master admin if I want to. The basic layout of the page will remain the same with the main content of the page used by the CMS system. I would like the site to have four template files that make up each page. The header, the left column menu, the main page area and the footer. The header and footer will not form part of the CMS. Hope all that makes sense and please PMB me with any questions.