Special files
This information is valid for Horde 3 only. See <a href="https://wiki.horde.org/Doc/Dev/SpecialFilesH4">Doc/Dev/SpecialFilesH4</a> for Horde 4 or <a href="https://wiki.horde.org/Doc/Dev/SpecialFiles">Doc/Dev/SpecialFiles</a> for Horde 5 and later.
- horde/lib/core.php: This file
    - sets some required PHP configuration settings
    - loads libraries required by all Horde applications
    - instantiates the global Browser object
There are several files with a special meaning that can be found in every Horde application:
- index.php: This script is loaded if a user enters an application. Usually this script doesn't have any functionality but simple loads the default view of the application, sometimes depending on the user's preferences.
- lib/base.php: This file is loaded from every script of the application. Its purpose is to:
    - define some global constants
    - load core.php
    - initialize the <a href="https://wiki.horde.org/Doc/Dev/RegistryH3">Registry</a>
    - redirect to the login screen if the user is not authenticated and guest access is disabled
    - load common Horde libraries
    - initialize the <a href="https://wiki.horde.org/Doc/Dev/Notification">Notification System</a>
    - load common application specific libraries
    - initialize common global application specific objects and variables
    - start output compression
- lib/api.php: This files defines and implements all methods that an application is exposing through the <a href="https://wiki.horde.org/Doc/Dev/RegistryH3">Registry</a> to the other Horde applications and the Horde RPC servers.
- lib/version.php: This files defines a single constant: the application's version number.
- templates/common-header.inc: This is the common page header template for all scripts of the application. All applications use the same page footer template horde/templates/common-footer.inc.
- themes/screen.css: This is a CSS file that defines all application specific style sheet rules.