Access Control System - Design

Hi,

I need to implement a "Access Control System", but I don't have any clue of
what it is the ideal system... I will try to explain my problem...

I have 4 levels of users in my web application, "Super Administrator",
"Administrator", "Manager" and "Worker".

The database have data from more than one company. But all different
companies belong to the same group of bussiness.

So... the . "Super Administrator" will access to the data of all companies
. "Administrator" will access to the data of only one
company(his company)
. "Manager" will access to the data of a region of only one
company AND all actions must be confirmed by the "Administrator".
. "Worker" will access only to the data that he inserts to the
system AND all actions must be confirmed by the "Manager" of his region.

Here I have the requirements of the "Access Control System" and the
requirements of the "Workflow".

I have read this document, but I don't know wich system to use. Here is the
document:
http://www.tonymarston.net/php-mysql/role-based-access-control.html

What is your advice for me? There are some open-source systems ready to use?

Best Regards,
André.