Open Source Document Management System (DMS) in PHP?

Hey Experts,

I currently have a simple FTP site setup in IIS with simple security rights on the FTP folder, but as you probably already know, it is very limited in terms of security, document searching, etc.

I need a simple open source DMS preferrably written in PHP that I can install on my in-house server and run as a website. Here are some of the features I require:

- Anonymous users can view the documents (pdf, docs, images) and search - no login needed (will be viewed by 1000+ users).
- Admins can add users, assign rights, upload, create groups, delete documents
- Authenticated users can upload/delete documents - login needed.
- Search capabilities.

Any suggestions???

Thanks in advance