How Joomla! Works

Sep 12, 2011

📄 Contents

␡

What's In This Chapter
Tour of Joomla! Folders
Joomla Platform
Web Programming vs. "Normal" Programming
Anatomy of a Joomla! Command Cycle
Let's Ask Louis: Including PHP Files
Naming Conventions (Conventional Wisdom?)
Global Objects
Overview of Database Tables

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From the Rough Cut 

Joomla! Programming

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Overview of Database Tables

Joomla uses a database (normally run with the MySQL database program) to store all of the data for the site. The standard Joomla database for version 1.6 contains 33 tables. In this section, we will give a brief description of each table and its role in the program.

Note About Table Prefixes

When you install Joomla, you can select a prefix for the table names in the database. The default prefix is "jos_". When you see a table accessed inside the PHP code, you will normally see it with the generic prefix "#__". The "query()" method of the "JDatabaseMySQLi" class calls a method called "replacePrefix()" that replaces the generic prefix with the actual one from the "configuration.php" file.

For the purposes of this book, we will use the default "jos_" prefix for the table names (for example, "jos_content"). However, in the code they will also be shown with the "#__" prefix (for example, "#__content"). If you specify a different prefix when you install Joomla, in your database the tables will be named with that prefix.

Standard Joomla Tables

Table Name	Description	PHP Class
jos_assets	New table added for ACL in version 1.6. Includes a row for every component, Contains a row for every item that has ACL permissions. This includes a "Root Asset" for the global permissions, a row for every component, plus a row for every component category, and finally a row for every article. The "rules" column stores the group permissions in JSON format. This table is used whenever we check if a user is authorized to perform an action.	JTableAsset
jos_banners	Contains a row for every banner defined in the site.	none
jos_banner_clients	Contains a row for every banner client defined in the site.	none
jos_banner_tracks	Contains a row for every banner track defined in the site.	none
jos_categories	Contains a row for every category defined in the site. This includes article, banner, contact, newsfeed, and weblinks categories.	JTableCategory
jos_contact_details	Contains a row for every contact defined in the site.	none
jos_content	Contains a row for every article defined in the site.	JTableContent
jos_content_frontpage	Contains a row for every article assigned to the featured blog menu item.	none
jos_content_rating	Contains a row for every rated article in the site.	none
jos_core_log_searches	Contains a row for every search term logged by the site.	none
jos_extensions	Contains a row for every extension installed in the site. This includes component, library, module, plugin, template, language, and file extensions.	JTableExtension
jos_languages	Contains a row for every language installed in the site.	JTableLanguage
jos_menu	Contains a row for every front and back-end menu item defined for the site.	JTableMenu
jos_menu_types	Contains a row for every front-end menu defined for the site.	JTableMenuType
jos_messages	Contains a row for every private message sent in the site.	none
jos_messages_cfg	Contains a row for every back-end user who sets a configuration in the Components → Messaging → My Settings option.	none
jos_modules	Contains a row for every module defined in the system. A "client_id" column of "0" indicates it is a front end module, "1" indicates a back-end module.	JTableModule
jos_modules_menu	Mapping table to show which modules are assigned to which menu items. The "menuid" column indicates which menu items the module is assigned to, as follows: "0" means assigned to all menu items; positive integer means assigned to this one menu item; and negative integer means assigned to all menu items except for this menu item.	none
jos_newsfeeds	Contains a row for every newsfeed created in the site.	none
jos_redirect_links	Contains a row for every redirect created in the site.	none
jos_schemas	Contains a row for each extension that has made database changes during its installation, along with the latest installed version of the extension.	none
jos_session	Contains a row for every active session for the site.	JTableSession
jos_template_styles	Contains a row for every template style defined for the site.	none
jos_updates	Contains a row for every available package to be installed.	JTableUpdate
jos_update_categories	This table is used to categorize the updates. It is maintained automatically by Joomla.	none
jos_update_sites	List of update sites. This comes from the update XML file for each extension.	none
jos_update_sites_extensions	Mapping table that links jos_extensions with jos_updates. Contains a row for each combination of extension and update site where that extension can be updated.	none
jos_usergroups	Contains a row for every user group defined for the site.	JTableUsergroup
jos_users	Contains a row for every user defined for the site.	JTableUser
jos_user_profiles	Contains a row for every combination of user id and profile field. This table is used if you have the User – Profile plugin enabled.	none
jos_user_usergroup_map	Contains a row for every group that a user is a member of.	none
jos_viewlevels	Contains a row for every View Level defined in the site.	JTableViewlevel
jos_weblinks	Contains a row for every weblink defined in the site.	none

Figure 46: List of Joomla Database Tables

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