Suggest me a good, free, open source, downloadable web application in php to make a good website for a organization or group having more than one member. Only administrator(s) can change the content of the website. Please do not suggest me any forum/blog applications like WordPress, phpBB etc. 
Web-Application to create organization/group website
webapp rec
Use one of the better-supported open-source CMSes for this reason.I would suggest either Drupal or Joomla, both written in PHP. I am a strong Drupal fan, but Joomla has a lot of supporters as well. Just some main bullet-points from the website of Drupal to show how versatile/powerful it is:General featuresCollaborative Book - Our unique collaborative book feature lets you  setup a book and then authorize  other individuals to contribute  content.detailed informationFriendly URLs - Drupal uses Apache's mod_rewrite to enable  customizable URLs that are both user  and search engine friendly.Modules - The Drupal community has contributed many modules which provide  functionality that extend Drupal  core.detailed informationOnline help - Like many Open Source projects, we can't say that our  online help is perfect but have built  a robust online help system built into  the core help text. Available to you  on your own site.detailed informationOpen source - The source code of Drupal is freely available under the  terms of the GNU General Public  License 2 (GPL). Unlike proprietary  blogging or content management  systems, Drupal's feature set is fully  available to extend or customize as  needed.detailed informationPersonalization - A robust personalization environment is at the  core of Drupal. Both the content and  the presentation can be individualized  based on user-defined preferences.Role based permission system - Drupal administrators don't have to  tediously setup permissions for each  user. Instead, they assign permissions  to roles and then group like users  into a role group.screenshot .  detailed informationSearching - All content in Drupal is fully indexed and searchable at all  times if you take advantage of the  built in search module.User managementUser authentication - Users can register and authenticate locally or  using an external authentication  source like Jabber, Blogger,  LiveJournal or another Drupal website.  For use on an intranet, Drupal can  integrate with an LDAP server.detailed  informationContent managementPolls - Drupal comes with a poll module which enables admins and/or  users to create polls and show them on  various pages.detailed informationTemplating - Drupal's theme system separates content from presentation  allowing you to control the look and  feel of your Drupal site. Templates  are created from standard HTML and PHP  coding meaning that you don't have to  learn a proprietary templating  language.detailed informationThreaded comments - Drupal provides a powerful threaded comment  model for enabling discussion on  published content. Comments are  hierarchical as in a newsgroup or  forum.detailed informationVersion control - Drupal's version control system tracks the details of  content updates including who changed  it, what was changed, the date and  time of changes made to your content  and more. Version control features  provide an option to keep a comment  log and enables you to roll-back  content to an earlier  version.screenshotBloggingBlogger API support - The Blogger API allows your Drupal site to be  updated by many different tools. This  includes non-web browser based tools  that provide a richer editing  environment.detailed informationContent syndication - Drupal exports your site's content in RDF/RSS  format for others to gather. This lets  anyone with a News Aggregator browse  your Drupal sites feeds.detailed  informationNews aggregator - Drupal has a powerful built-in News Aggregator for  reading and blogging news from other  sites. The News Aggregator caches  articles to your MySQL database and  its caching time is user  configurable.detailed informationPermalinks - All content created in Drupal has a permanent link or  perma link associated with it so  people can link to it freely without  fear of broken links.PlatformApache or IIS, Unix / Linux / BSD / Solaris / Windows / Mac OS X support  - Drupal was designed from the start to be multi-platform. Not only can you  use it with either Apache or Microsoft  IIS but we also have Drupal running on  Linux, BSD, Solaris, Windows, and Mac  OS X platforms.detailed informationDatabase independence - While many of our users run Drupal with MySQL, we  knew that MySQL wasn't the solution  for everyone. Drupal is built on top  of a database abstraction layer that  enables you to use Drupal with MySQL  and PostgreSQL. Other SQL databases  can be supported by writing a  supporting database backend containing  fourteen functions and creating a  matching SQL database scheme.detailed  informationMulti-language - Drupal is designed to meet the requirements of  an international audience and provides  a full framework to create a  multi-lingual website, blog, content  management system or community  application. All text can be  translated using a graphical user  interface, by importing existing  translations, or by integrating with  other translation tools such as the  GNU gettext.detailed informationAdministration and analysisAnalysis, Tracking and Statistics - Drupal can print browser-based reports with information about  referrals, content popularity and how  visitors navigate your site.screenshot  . detailed informationLogging and Reporting - All important activities and system events  are captured in an event log to be  reviewed by an administrator at a  later time.screenshot . detailed  informationWeb based administration - Drupal can be administered entirely using a  web browser, making it possible to  access it from around the world and  requires no additional software to be  installed on your computer.screenshotCommunity featuresDiscussion forums - Full discussion forum features are built  into Drupal to create lively, dynamic  community sites.detailed informationPerformance and scalabilityCaching - The caching mechanism eliminates database queries increasing  performance and reducing the server's  load. Caching be tuned in real time  and many high-traffic sites have  performed very well under  load.detailed information