Drupal:
Under the Hood

What is Drupal?
1. Content Management System
2. Content Management Framework
3. Community

Content Management
System

file
uploads
revisions menus
security user profiles
blocks performance modules search
engine-friendly urls user manage-
ment administration panels localization error
reporting rss taxonomy blogging comments
forums multi-site installations event
logging community authoring ajax search
free tagging feed aggregation contact
form help system roles and per-
missions statistics
tracking polls

1200+ Contributed
Modules

Community

Doubles in size each
release
source: http://acko.net/blog/drupal-org-explosion-and-trends source: http://buytaert.net/drupal-site-statistics

Statistics
• 840+ code contributors
• 160+ local user groups
• 430+ attendees at Drupalcon Barcelona
• 200,000+ users on drupal.org
• 3 million+ lines of code (core+contrib)
• 52 SoC mentors for 20 students
• 100,000+ downloads/month

Content Management
Framework

xml-rpc
file api jquery
database abstraction layer form
api file api session management node
system url routing theme system string
handling filter system content versioning
installation profiles access control trans-
latable output user system caching
date/time handling unicode support mail
handling image manipulation installation
system hook system menu system
module system user authentication
themable output

What’s under the hood?

Core
• Lightweight framework
Drupal Core
• Library of common Content User
Forms API
Management Management
functions
Install Theming
•
Localization
Allows Drupal to Profiles Layer
bootstrap and serve a
request
Library of Common Functions
• What you get when you
download Drupal

Modules
Drupal Core
Content User
Forms API
•
Management Management
How Drupal is extended
Install Theming
Localization
•
Profiles Layer
Lean and mean and
versatile
•
Library of Common Functions
Inversion of control design
pattern
Modules
• Actions/ Content
Drupal exposes hooks Ecommerce
Workflows Creation Kit
for modules
Organic
Views
Groups
Custom
Module

INSTALL.txt index.php themes
install.php update.php modules
sites xmlrpc.php includes

drupal_bootstrap()
• DRUPAL_BOOTSTRAP_CONFIGURATION
• DRUPAL_BOOTSTRAP_EARLY_PAGE_CACHE
• DRUPAL_BOOTSTRAP_DATABASE
• DRUPAL_BOOTSTRAP_ACCESS
• DRUPAL_BOOTSTRAP_SESSION
• DRUPAL_BOOTSTRAP_LATE_PAGE_CACHE
• DRUPAL_BOOTSTRAP_PATH
• DRUPAL_BOOTSTRAP_FULL

menu system

Yes
Is site Return
offline? MENU_SITE_OFFLINE
No
Get menu array
Is callback No
Parse $path from Trim last '/' from
defined for
$_GET['q'] $path
$path?
No
Does callback Return
function exist? MENU_NOT_FOUND
User allowed
No Return
to access this
MENU_ACCESS_DENIED
item?
Marshall parameters
from URL and item's Call callback
callback arguments

Hooks

Hooks are PHP functions
with Drupal-specific names

How Drupal Finds Hooks
/**
* Determine whether a module implements a hook.
*
* @param $module
* The name of the module (without the .module extension).
* @param $hook
* The name of the hook (e.g. \"help\" or \"menu\").
*/
function module_hook($module, $hook) {
return function_exists($module .'_'. $hook);
}

Naming Hooks
Module Hook Function name
pants user pants_user()
pants menu pants_menu()
pants perm pants_perm()

Hook Overview
hook_user()
comment_user() locale_user() node_user() mymodule_user()
comment.module locale.module node.module mymodule.module

FormAPI

FormAPI
• Form elements are PHP arrays so you can
programmatically manipulate any form
• Chain validator and submitter routines
• Theme overrides - down to the element!
• Built-in security

Form Example
$form['user_name'] = array(
'#title' => t('Your Name'),
'#type' => 'textfield',
'#description' => t('Please enter your name.'),
);
$form['submit'] = array(
'#type' => 'submit',
'#value' => t('Submit')
);

Security
• Verifies that $_POST values have
corresponding $form elements
• Form rendering sanitized for potential XSS
• $form[‘token’] used to prevent CSRF

hook_form_alter

drupal_execute()

Theme System

Theme System

PHPTemplate Files
• page.tpl.php
• node.tpl.php
• block.tpl.php
• comment.tpl.php
• box.tpl.php

theme('breadcrumb')
theme-name_breadcrumb()
theme-engine_breadcrumb()
theme_breadcrumb()
The first
function found
gets called.

theme('page')
garland_page()
phptemplate_page()
theme_page()
The first
function found
gets called.

Creating New Template Files
template.php
function mytheme_breadcrumb($breadcrumb) {
if (!empty($breadcrumb)) {
return '<span class=\"breadcrumb\">'. implode(' * ', $breadcrumb) .'</span>';
}
}
new template.php
function mytheme_breadcrumb($breadcrumb) {
if (!empty($breadcrumb)) {
$variables = array('breadcrumb' => implode(' * ', $breadcrumb));
return _phptemplate_callback('breadcrumb', $variables);
}
}
breadcrumb.tpl.php
<span class=\"breadcrumb\"><?php print $breadcrumb ?></span>

ultimate control

http://greenpeace.co.uk/

http://theonion.com/

http://musicbox.sonybmg.com/

http://43folders.com/

http://lifetimetv.com/

http://flex.org/showcase

http://help.yahoo.com/

http://ubuntu.com/

Thanks... Questions?
James Walker
http://walkah.net/
Lullabot
james@lullabot.com