Drupal is a free and open source modular framework and content management system (CMS) written in the programming language PHP. Like many modern CMSs, Drupal allows the system administrator to create and organize content, customize the presentation, automate administrative tasks, and manage site visitors and contributors.
Drupal is sometimes described as a "Content Management Framework as its capabilities extend from content management to enabling a wide range of services and transactions. Although Drupal does offer a sophisticated programming interface, basic web site installation and administration can be accomplished with no programming.
Drupal runs in many environments, including Windows, Mac OS X, Linux, FreeBSD, OpenBSD, Solaris 10, OpenSolaris and any platform that supports either the Apache (version 1.3+), or IIS (version IIS5+) Web server and the PHP language (version 4.3.5+). Drupal requires a database such as MySQL or PostgreSQL to store content and settings.
Originally written by Dries Buytaert
as a bulletin board system
, Drupal became an open source
project in 2001. Drupal
is an English rendering of the Dutch
,” which means “drop” (as in “a water droplet”). The name was taken from the now-defunct Drop.org website, whose code slowly evolved into Drupal. Buytaert wanted to call the site “dorp” (Dutch for “village,” referring to its community aspects), but made a typo when checking the domain name and thought it sounded better.
From May 2007 to April 2008, Drupal was downloaded from the Drupal.org website more than 1.4 million times, an increase of approximately 125% from the previous year. A large community now helps develop Drupal.
As of August 2008, Drupal 6.4 is the latest release. Drupal is a winner of several Packt Open Source CMS Awards.
The official release of Drupal, known as "Drupal core", contains basic features common to most CMSs. These include the ability to register and maintain individual user accounts, administration menus, RSS
-feeds, customizable layout, flexible account privileges, logging, a blogging
system, an Internet forum
, and options to create a classic "brochureware
" Web site or an interactive community Web site.
Web site content can be contributed by registered or anonymous users (at the discretion of the administrator), and made accessible to Web visitors by a variety of criteria including by date, category, searches, etc. Drupal core also includes a hierarchical taxonomy system which allows content to be categorized or "tagged" with keywords for easier access.
Drupal maintains a detailed changelog of core feature updates by version.
Drupal core also includes "core modules" which can be enabled by the administrator to extend the stock functionality of the core Web site.
The core Drupal distribution provides a number of features, including:
- Access statistics and logging
- Advanced search functions
- Caching and feature throttling for improved performance under load
- Comments, forums, and polls
- Descriptive URLs (for example, "www.example.com/products" rather than "www.example.com/?q=node/432")
- Multi-level menu system
- Multi-user content creation and editing
- OpenID support
- RSS Feed and Feed Aggregator
- Security/new release update notification
- User profiles
- Various access control restrictions (user roles, IP addresses, email)
- Workflow tools (Triggers and Actions)
Drupal core includes several "core themes", which customize the aesthetic look-and-feel of the site. These themes can be chosen by the administrator via a special menu.
The Color Module, introduced in Drupal core 5.0, allows administrators to change the color scheme of certain themes via a Web-browser interface. This feature was added to allow a higher level of customization for the average non-coder.
As of February 2008, translations for Drupal's interface were available in 44 languages plus English (the default). Some read right to left, such as Arabic and Hebrew. Drupal 6 provides improved support for content and content administration in multiple languages.
Beginning in version 6.0, Drupal can automatically notify the administrator when a new version of a contributed module, theme, or the Drupal core itself, becomes available. This is a feature which may help to keep a Drupal installation up-to-date with the latest features and security fixes.
A module for version 5.x provides identical functionality, but it is not included in the core release.
Extending Drupal core
Drupal core is designed to be modular
with a system of "hooks
" and "callbacks
", which are accessed internally via an API
. This design allows third-party "contributed" (often abbreviated to "contrib") modules
to extend or override Drupal's default behaviors without changing Drupal core's code.
Drupal's modular design, which isolates Drupal core's files from contributed module and themes, increases flexibility and security and allows Drupal administrators to cleanly upgrade to new releases of Drupal core without potentially overwriting their site's customizations. To maintain this separation, Drupal administrators are instructed to avoid altering Drupal core's software.
Contributed Drupal modules offer a variety of features including image galleries, custom content types and content listings, WYSIWYG
editors, private messaging, 3rd-party integration tools, and more. The Drupal Web site lists 2332 free modules
(as of June 1
), written and contributed to by the Drupal community.
Two modules are particularly important to typical Drupal installations:
- Content Construction Kit (CCK) allows site administrators to dynamically create content types. A content type describes any kind of information to be stored in the Web site's database. These may include, but are not limited to, events, invitations, reviews, articles, or products.
- Views facilitates the retrieval and presentation of content to site visitors.
The CCK API is scheduled to be integrated into Drupal as a core module starting with Drupal 7, and Views (without its user interface) will follow at some point thereafter.
Contributed themes adapt or replace a Drupal site's default look and feel.
Drupal themes use standardized formats that may be generated by common third-party theme design engines. Many themes for Drupal are written in the PHPTemplate engine or, to a lesser extent, the XTemplate engine. Some templates use hard-coded PHP.
Although early versions of Drupal's theming system were criticized for being less design-oriented and more complicated than those for Mambo, Joomla! and Plone, the inclusion of the PHPTemplate and XTemplate engines in Drupal has addressed some of these concerns. The new Drupal 6 theming system utilizes a template engine in an attempt to further separate HTML/CSS from PHP. A new Drupal development module, Devel, provides assistance to theme authors who use Drupal 6.
Community contributed Drupal themes at the Drupal web site are released under GPL license (free), and most of them are demonstrated at the Drupal Theme Garden.
Lack of object orientation
Drupal exclusively uses procedural programming
, not object-oriented programming
(OOP). While Drupal approximates some of OOP's features, its lack of OOP results in the following:
- No encapsulation enforced by the underlying programming language system. This precludes the use of private data and causes nonexistent enforcement of namespace separation.
- Less efficient code reuse since object inheritance is "weak" and polymorphism is only approximated in the rendering layer.
Drupal's defenders counter that even though PHP's OOP language features are not directly implemented (to ensure compatibility with older 4.x versions of PHP), OOP and aspect-oriented programming (AOP) principles are present in Drupal's design. This will help ease the transition to future versions of Drupal core, which, starting with version 7, will begin to take advantage of OOP provided by PHP 5. Drupal 7 will not be backwards compatible with prior PHP releases.
- Some aspects of Drupal's administration interface can be confusing and intimidating, particularly for new administrators. According to the Interaction Design and Information Architecture program at the University of Baltimore, Drupal lacks an intuitive, easy administration user interface. The administration area is regarded as clunky and cryptic with Drupal version 5 and 6, but improved ease of use is planned with the upcoming version 7. According to Dries, Drupal 7 won't be released until 90% of the problems identified by the University of Minnesotaand the University of Baltimore are solved. Usability will be one of the main improvements in Drupal 7 that will close the gap with easier CMS.
Steep initial learning curve
- Drupal may be powerful, but it is also complex. The key is overcoming its steep initial learning curve. Most casual users are willing to sacrifice features for ease of use making Drupal less popular than more user-friendly CMS's despite its enhanced functionality.
Security response record
From January to May 2008, five security vulnerabilities were reported and fixed in Drupal core. Security holes were also found and fixed in 25 of the 2147 user-contributed modules.
As security holes are discovered, Drupal core is regularly updated to new versions. Administrators of Drupal sites are automatically notified of these new releases via the Update Status module. Additionally, Drupal.org maintains a security announcement mailing list, a history of all security advisories, a security manual, and an RSS feed with the most recent security advisories.
Customized Drupal distributions include some repackaged third-party modules, some with modifications to the core, including vbDrupal
, which is Drupal integrated with vBulletin
Drupal 4.2 was used for DeanSpace
, which hosted many independent Web sites supporting the 2004 presidential campaign of Howard Dean
. After the Dean campaign ended, the DeanSpace project grew into CivicSpace
, a Drupal-based "grassroots organizing platform that empowers collective action inside communities and cohesively connects remote groups of supporters." Thus CivicSpace is a spinoff distribution originally based on Drupal 4.2.
Many innovations in CivicSpace have been incorporated back into the Drupal project itself. Features particularly useful for nonprofit organizations and political campaigns are provided in the CiviCRM module for Drupal 5.0 and higher.
It has been suggested to distribute "pre-made" Drupal installations that are pre-customized with third party modules and configured towards a particular type of Web site: an online store, a music review site, a blogging site, etc. Drupal 5.x goes in this direction, providing a set of "installation profiles" tailored to specifics goals.
In 2007, a Drupal-focused company, Acquia
, was created by Drupal project lead Dries Buytaert
and Jay Batson
. Acquia announced a subscription-based service for Drupal at Drupalcon Boston 2008 and started services with Acquia Drupal
, a distribution based on Drupal 6, in September 2008. Subscriptions include one or more Drupal distributions, a set of companion network-supplied value-add services, and access to a Technical Assistance Center.
Drupal has a large community of users and developers. More than 350,000 user accounts have been created on Drupal.org, and over 2000 people have signed up for developer accounts. The last major conference in the USA, Drupalcon Boston 2008, attracted over 800 people.. The last European conference, Drupalcon Sgezed 2008, held in late August 2008, had an attendance of 500.
There are a number of active Drupal forums, mailing lists, and discussion groups. Drupal also maintains several IRC channels on the Freenode network.
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