There are many similar programs but PHP-Nuke is designed to be very customizable and flexible, is easy and pleasant to use, thinking about webmasters who pass hours administrating his web site.
PHP-Nuke also offers a very high number of features not present on other systems and on each release we'll add much more new and cool features.
The main aim of PHP-Nuke is to allow a webmaster to create a community-based portal, with an automated web site allowing users and editors to post news items (user-submitted news items are selected by editors). Users can comment on these articles using the comments system. Modules may be added to the PHP-Nuke system, allowing the webmaster to add more features (such as an Internet forum or calendar) to their PHP-Nuke installation in addition to the core modules such as News, FAQ and Private Messaging. The whole system is maintained by administrators using the web-based administration section.