PHP Application recommendation for Group Blog

["Roger Vicker, CCP" <rv-tech@xxxxxxxxxx>]

Hello,

I am looking for recommendations for a PHP application that a group can
use as a cross between work flow and blog.

The requirements are:

1) Can be viewed by registered members only. No public reading.
2) Once an item has been posted (Blog story...) each of the other users
can respond (comment...) but can not change/remove their responses.
3) Email notice of new Items.
4) Users have to be setup or approved by an administrator. Did I mention
absolutely no public access?
5) Maximum portability. PHP, MySQL, no need for command line or shell
access.

I've looked at WordPress but didn't see a simple (as in the users) way
to completely restrict access. Yes, the folder can be password protected
but that would add another user/password level for the users to fight with.

Thanks.

Roger Vicker, CCP