1. Intro To Drupal Module Internals Greg Monroe Longsight, Inc.
Triangle Drupal Users Group
2. How will this help? Drupal is user contributed. This means
that documentation is often lacking. The people writing modules
generally say Read the code Knowing some basics about Drupal module
internals, even if you can't program, will help you use even the
worst documented module.
3. Skills and Tools A very basic knowledge of PhP (e.g. can
kinda follow the basic logic but may not be able to write it) A
decent (plain) text editor ( e.g. Notepad++, Text Edit, Gedit )
Optionally, you could find a more PhP friendly editor that displays
a function list and allows for searching thru multiple
file/directories. (SciTE, Geany, NotePad++ with plugins, Eclipse,
Aptana, Zend)
4. How modules work Core finds them via modules admin page
Stores info about them in System DB table Enabling module sets flag
in System DB table, creates required DB tables, does initial setup
and registration duties. Main code for enabled modules loaded at
page boot by core. Module code gets called via hooks by core and
other modules Module Magic happens
5. What are Hooks Drupal is based on hooks Modules use them to
extend Drupal and to extend themselves. Hooks are associated with
key actions, e.g. saving a node. When a hook action happens, core
or a module with hooks calls all modules that have implemented the
hook for that action.
6. Some Hook Fundamentals Hooks are documented like hook_name,
e.g. hook_block_info Modules implement hooks as functions with
names that replace hook with the module name. E.g, the foo module
would implement hook_menu as foo_menu Core hooks usually are in
*.module files
7. POP QUIZ If you read something like: The foo module uses
hook_menu to do that What name will this hook use?
8. Answer: This translates into a function with the form:
foo_menu E.g.: function foo_menu() { Extra credit for knowing it
might be in the foo.module file.
9. Additional Reading A good place to start learning about core
hooks is http://api.drupal.org/ Search for Hooks for the main page
or search for hook_ for a specific hook.
10. Useful Module Splunking Hooks Hook_help Hook_menu
Hook_block_info Hook_theme Hook_permision Hook_views_api Note: You
can find full documentation on hook by googling: Drupal api
hook_
11. Module Directory Files for a module will be under a common
directory. The name of this directory is the module's basename.
E.g., Organic group is og and Node Gallery uses node_gallery Note:
Module base directories can exist under other modules, e.g.
og_views is found in og/modules/og_views
12. Module Files Required: .info .module Recommended:
README(.txt) LICENSE(.txt) .install Naming Conventions: *.inc
Include files loaded as needed *.pages.inc code needed for general
pages *.admin.inc code needed for admin pages *.tpl.php
Override-able theme template files *.api.php Documents the hooks
this module has
13. An Example of Module files The Organic Group Module
14. Finding a Module Finding a module that is creating some
page or block from the displayed page is hard and beyond this talk
If you know the Human name, e.g. Organic Groups, you can find the
base name from the drupal.org/project/ URL. Knowing this, see if
you can download it from Drupal.org. Looking at a module outside
your web server is MUCH safer. But if you think your sites code is
custom or you cant find the Drupal Project.
15. Wheres Wald..err.. the Module Modules can live many places
but by convention they generally live under one of three
directories: /modules (Core only!) /sites/all/modules (for all
sites) /sites/default/modules Note: In multisite setups, the
sites/default part above may be your host name, e.g.
sites/www.my.com Next check to see if a basename directory exists
if not, use a file search tool to look for .info under these
directories.
16. The .info file The module.info file contains: Basic
description of the module. Dependencies Object class files used by
this module. CSS and Script files Configure URL
17. The .Module File The .module file contains the core code
for the module and generally all the hooks were interested in.
18. Finding Hooks With the .module file in an editor: If your
editor show functions, just look for the _ postfix, e.g. _menu
Search for hook_, e.g. hook_menu Search for _, e.g. og_menu Look
for _, e.g. _menu
19. Hook_Help Notes: Supplies text for Drupal Advanced help
system Case statements URL help applies to Return statements - Help
text
20. Hook_Menu Notes: Defines URLs (as menu items or just pages)
for pages the module creates $items[] statements URL of page - %xxx
indicate argument substitution title array key - Menu/Page title
page callback array key - function to create page access callback
array key - function that determines access
21. Hook_Block_Info Notes: - Defines blocks this module adds -
info array key is name shown in block admin display The block_view
hook defines how the block contents are created The block_configure
hook (not shown) defines any block specific configuration
options
22. Hook_Theme Notes: _xxx keys - These define the theme hooks
for this module arguments key - Defines the values passed to the
theme hook template key - Indicates this theme hook is a .tpl.php
template file path key - The directory the tpl.php file is located.
Code for non-template hooks will be in theme_ functions.
23. Hook_Permission Notes: Defines any module specific
permissions. Note that many modules use PhP constants to define
permissions. So, look at these to get the names used in the
permission settings screens.
24. Hook_views_api If you find this hook, you know that this
module supports views and might be supplying blocks and pages thru
code embedded views it installs. The path option will indicate
where the views related .inc files will live. If you look thru
these you will generally find the names of views this module
creates. Other places to look for views information is in the
Module .info file.
25. Some Advanced Hooks hook_node_* A set of hooks to modify
the node save, display and load options. hook_user_* A set of hooks
to modify user actions, e.g. load, save, display, login, etc.
hook_form_alter Allows any Drupal form to be modified by another
module hook_schema Defines database tables used by this Module.
This will be in the .install file. hook_cron Defines any cron jobs
a module needs hook_*_alter Functions of this form generally are
using a hook to alter something that core or a module
provides.
26. Questions / More Info The book Pro Drupal Development is a
good reference Drupal API site has lots of docs on hook
DrupalContrib.org has lots of docs on non- core hooks Of course
Drupal.org and general search will help you find lots of good
stuff. Especially if you search for hook_
