"Fossies" - the Fresh Open Source Software Archive 
"Fossies" - the Fresh Open Source Software Archive A hint: This file contains one or more very long lines, so maybe it is better readable using the pure text view mode that shows the contents as wrapped lines within the browser window.
The relevant architecture of serendipity (s9y) depends on the entry point. A regular visitor of a blog will be served by the index.php, which chains file after file via include together to decide which page to render. The backend is served by serendipity_admin.php, while the feeds come from rss.php, and comment.php is where comments, trackbacks and pingbacks are received.
All of these entry points work with the general file structure of the software. include/ contains the thematically grouped functions that other code can call. include/admin/ is where the main code for backend pages live, the code there does the work related to the request and at the end decides which page to render. The HTML generation for frontend and backend is done via smarty template files located under templates/, with 2k11 being the default theme used. The files under templates/2k11/admin/ will generate the backend (if the chosen theme does not come with a custom admin backend), the files in the folder above the frontend pages regular visitors see.
When a request is served by the index.php, broadly
this happens: The index.php will use regular
expressions (partly configurable by the user) to decide which routing
function has to react. Most of those call
include/genpage.inc.php and set some parameters in the
$serendipity global. genpage.inc.php
decides based on $serendipity['GET']['action'] what to do,
and either prints a specific blog entry or multiple or e.g. the search
page with search results. serendipity_printEntries is the
main function to print articles given to it, it will call the smarty
templates defined under the currently used theme (fallback if a file is
missing: 2k11), and serendipity_fetchEntries is the main
function that gets entries from the database.
A request served by serendipity_admin.php, after the
login status check, is treated depending on
$serendipity['GET']['adminModule']. The value is mapped to
the files in include/admin, which are then included.
Those look at $serendipity['GET']['adminAction'], do the
work and call the .tpl files under
2k11/admin/ to generate the HTML. The backend Javscript
is generated by the serendipity_editor.js.tpl.
Throughout all flows, the global $serendipity is filled
with information. It holds a lot of the needed information about the
current state, blog configuration and the request parameters. It is also
read a lot and can thus be used to transmit information to later
sections of the program flow. Please use this sparingly in new code.
The plugin system is rather powerful. Calls to
serendipity_plugin_api::hook_event('event_name', $eventData, $addData)
are sprinkled throughout the whole code. That function then iterates
through all event plugins under plugins/, so those
plugins that have registered the called event can run their PHP code.
For example, anti-spam plugins will be given submitted comments, do
their work and then signal via the plugin layer and the
$serendipity global whether the plugin should be saved and
shown, saved and moderated or completely denied. And plugins cann add to
the javascript and css served in the frontend via the js and
css plugin events.
Sidebar plugins instead are called whenever a page with a sidebar in
the frontend is generated. They can not register multiple events. They
can only emit HTML via their generate_content function.
Serendipity supports multiple database engines, the main ones being
MySQL, SQLite and PostgreSQL. Serendipity will include
include/db/db.inc.php, that file will then include
include/db/{$serendipity['dbType']}.inc.php.
$serendipity['dbType'] is set in
serendipity_config_local.inc.php, a file generated
during installation.
Always when s9y has to talk to the database it will do so via the
function serendipity_db_query or
serendipity_db_schema_import, functions defined in the
included database layer file and adapted for their respective database
engine. serendipity_db_schema_import can replace parts of
the SQL query with specific expressions for their database layer. It
will for example replace {BOOLEAN} to something that works
in all supported database engines (SQLite for example has no boolean
database type, PostgreSQL does).