Intro to Drupal Module Internals

Intro To DRUPAL Module Internals
Greg Monroe
Triangle Drupal Users Group
Aug 11, 2011

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…)

What we won’t cover
Finding modules
Downloading modules
Installing modules
Enabling modules
Configuring module

What will be covered
How Modules work overview
Basic module file structure
Finding modules
The .info file
The .module file
Finding help in the module
Finding module menu items (pages)
Finding blocks a module supplies
What does the module allows to be themed
Finding permissions
Finding views the module creates

How modules work
Core finds them via admin/build/module
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 modules loaded at page “boot”.
Module code gets called via “hooks” by core and other modules
Module Magic happens

Some Hook Fundamentals
There are many hooks from many sources but a good starting place is:http://api.drupal.org/api/drupal/includes--module.inc/group/hooks/6
Hooks are generally documented as hook_name, e.g. hook_menu or hook_block
Hooks implementations are basically functions that follow a specific naming format. So, for the “foo” module to implement hook_menu, it must have a function named, foo_menu.

Useful Module Splunking Hooks
Hook_help
Hook_menu
Hook_block
Hook_theme
Hook_perm
Hook_views_api
Note: You can find full documentation on hook by googling:
“Drupalapi hook_<name>”

Module File Structure
All module files live under a common directory, who’s name is the module “basename”. E.g., Organic group is “og”, Node Gallery uses node_gallery, CCK uses content.Note: Module base directories can exist under other modules, e.g. og_views is found in og/modules/og_views…
At a minimum, a module base directory needs two files: <basename>.info (e.g. og.info) <basename>.module (e.g. og.module)

An Example of Module files
The Organic Group Module

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 using FireBug and the Modules page. Just inspect the enable checkbox and look at the value.
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 site’s code is different or you can’t find the Drupal Project….

Where’s Wald..err..the Module
Modules can live many places… but by convention they generally live under one of three directories: <drupal root>/modules (Core only!) <drupal root>/sites/all/modules (for all sites) <drupal root>/sites/default/modulesNote: In multisite setups, the default part above may be your host name, e.g. www.my.comNext check to see if a basename directory exists… if not, use a file search tool to look for <basename>.info under these directories.

Module Files
Required:
<basename>.info<basename>.module
Recommended:
README(.txt)LICENSE(.txt)<basename>.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

The .info file
The module.info file contains the basic description of the module.

The .Module File
The <Basename>.module file contains the core code for the module and generally all the hooks we’re interested in.

Finding Hooks
With the .module file in an editor:
If your editor show functions, just look for the _<hook name> postfix
Search for “hook_<hook name>”
Search for <basename>_<hook name>
Look for _<hook name>

Hook_Help
Notes:
Supplies text for Drupal
Advanced help system
Case statements
– URL help applies to
Return statements
- Help text

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

Hook_Block
Notes:
If ($op == list) section
- Defines blocks this
module adds
‘info’ array key
– Name shown in block
admin display
The “view” op (not shown)
defines how the block
contents are created
The “configure” op (not
shown) defines any block
specific configuration
options

Hook_Theme
Notes:
‘<basename>_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_<name> functions.

Hook_Perm
Notes:
Defines the permissions this
module uses.
Note that many modules use
PhP constants to define
permissions. So, look at
these to get the names used
in the permission settings
screens.

Hook_views_api
If you find this hook, you know that this module supports views and might be supplying blocks and pages thru 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

Questions / More Info
Pro Drupal Development is the “bible”
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.

Intro to Drupal Module Internals

by cgmonroe on Aug 22, 2011

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Intro to Drupal Module Internals — Presentation Transcript