Introduction
Joomla! plugins serve a variety of purposes. As modules enhance the presentation of the final output of the Web site, plugins enhance the data and can also provide additional, installable functionality.
This tutorial looks at the general principles used to design and build a plugin.
Plugin Types
While the number of possible types of plugins is almost limitless, there are a number of core plugin types that are used by Joomla!. These core types are grouped into directories under
/plugins/. They are:
- authentication
- content
- editors
- editors-xtd
- search
- system
- user
- xmlrpc
Authentication plugins allow you to authenticate (to allow you to login) against different sources. By default you will authenticate against the Joomla! user database when you try to login. However, there are other methods available such as by OpenID, by a Google account, LDAP, and many others. Wherever a source has a public API, you can write an authentication plugin to verify the login credentials against this source. For example, you could write a plugin to authenticate against Twitter accounts because they have a public API.
Content plugins modify and add features to displayed content. For example, content plugins can cloak email address or can convert URL's into SEF format. Content plugins can also look for markers in content and replace them with other text or HTML. For example, the Load Module plugin will take {*loadmodule banner1*} (you would remove the *'s in practice. They are included to actually prevent the plugin from working in this article), load all the modules in the banner1 position and replace the marker with that output.
Editor plugins allow you to add new content editors (usually WYSIYWG).
Editor-XTD (extended) plugins allow you to add additional buttons to the editors. For example, the
Image,
Pagebreak and
Read more buttons below the default editor are actually plugins.
Search plugins allow you to search different content from different components. For example, search plugins for Articles, Contacts and Weblinks are already provided in Joomla!.
System plugins allow you to perform actions at various points in the execution of the PHP code that runs a Joomla! Web site.
User plugins allow you to perform actions at different times with respect to users. Such times include logging in and out and also saving a user. User plugins are typically user to "bridge" between web applications (such as creating a Joomla! to phpBB bridge).
XML-RPC plugins allow you to provide additional XML-RPC web services for your site. When your Web site exposes web services, it gives you the ability to interact remotely, possibly from a desktop application. Web services are a fairly advanced topic and will not be covered in much detail here.
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