Piwik should use autoload to automatically load the classes.
This would simplify the code, would make loading pages faster, as unecessary includes wouldn't be loaded, and would greatly increase reusability of the code.
For example, Zend does it via
see the code on http://www.google.com/codesearch/p?hl=en#1oUPVh-C1Wg/trunk/eval/gx/zendframework/library/Zend/Loader.php&q=%22spl_autoload_register(array($class,%27autoload%27))%3B&l=32
Once implemented we can remove all require_once from all .php files. The includes for the Piwik_* (core/PluginsFunctions/*) shortcut functions would still be required and could all be merged in one include file.
Suggests it would be as easy as adding this to index.php and piwik.php:
require_once 'Zend/Loader/Autoloader.php'; Zend_Loader_Autoloader::getInstance();
Silly me... RTFM, we would still have to define an autoloader callback to map classes in our namespace to actual files.
vipsoft, this ticket means: - using autoloading for all zend classes (if this is not already the case) by calling their autoloader - adding an autoloader in Piwik (can we somehow reuse the zend one?) and keep it as simple as possible (as in zend). This will most likely mean that a few classes will have to be moved/renamed. most classes should be OK as we used a similar structure to the zend structure.
(In ) refs #620 - class renaming for consistency
(In ) fixes #801, fixes #620 - implement autoloader; remove require_once FrontController.php from ./index.php to test autoloader; add "false" parameter to all class_exists() calls to not trigger autoloader
Confirming that  was a global search and replace, including tests/*.
(In ) refs #620, refs #803 - refactor autoloader into core/Loader.php (class Piwik_Loader); remove unnecessary require_once in core/Common.php