You can't find anyone who's tested and done a good documentation on it ?

Well let us first introduce it. The horde project (http://www.horde.org/) is a collection of quite complex PHP application that can work without a unchallenged variety of data systems : oracle or mysql databases, LDAP, etc... Everyhting in horde is Object Oriented, which basically means very reusable code.

Above data access classes which primarily relie on PEAR objects (pear.php.net), the root classes provide functionnality for building complex multi user applications :  dealing with preferences, compression, browser detection, connection tracking, MIME handling, and more.

Of course, and  unlike other projects of that size, horde is open source and does not seem to be the kind of project that will provide some free code just to make you hungry for the "professionnal" proprietary version. The spirit of opensource is here, and one example of that is the first project that a serious developper will need to participate to the Horde Project : Chora, which  is the Horde CVS viewer, and provides an advanced web-based view of any CVS repository. knowing the importance of CVS in terms of version control and code maintenance, we can see with that one that the issue is not a minor one within the Horde community.

You might have come across horde if you have used IMP, their famous email client. IMP is the example of a famous php based application that uses horde, but you'll find a complete list of official horde projects at
http://www.horde.org/projects.php

Horde is a tool for developers but existing applications are built for everyone. Installation is not hard, there is no need to write that what is written in the official and minimalistic INSTALL page shipped with every project. The only hard thing with horde is to find or build a LAMP (Linux / Apache Mysql PHP) that has all configuration requirements detailed in the INSTALL file. You can also have a look at these few links that just reformulate or extend the official INSTALL procedure :

• http://www.horde.org/horde/docs/?f=INSTALL.html
• http://www.linux-mag.com/2004-10/lamp_01.html
• http://www.totkat.org/pages/install-horde.shtml
  
  
  Good luck with the horde !