Glossary

access modifier In PHP, the words “public,” “protected,” or “private” may be used to control where class methods and fields may be accessed. Public fields and methods can be accessed from anywhere. Protected fields and classes can only be accessed from inside the current class or a parent or child of the current class. Private fields and classes can only be accessed from inside the current class. Note that private methods and fields are not inherited by child classes.

alias In Joomla!, a field for entities such as articles, menu items, and contacts, that are used to create search-engine-friendly URLs. Alias fields can be entered manually or created automatically based on the title of the entered item by removing characters other than lowercase letters, numbers, and dashes. For example, “The Joomla Project” creates an alias of “the-joomla-project.”

alternative menu item A modified core menu item that uses an override XML file and layout file to alter its display and function.

apache (apache HTTP server) The web server program used by most Joomla websites. The “A” in LAMPP.

API Application programming interface. The published methods for using a set of programs. In Joomla, the API refers to the public methods and fields of all the defined classes, especially ones in the Joomla platform. Because third-party programs rely on the API, it should be changed as infrequently as possible and always with advanced notice.

associative array PHP array stored in key-value pairs (for example, name => 'George', title => 'President').

boolean Type of variable in PHP that can only be true or false.

class In object-oriented programming, the programming code that defines a class. A class defines an object type and can have fields and methods. In Joomla, each class is normally defined in its own PHP file.

column (database column) One type of data for a database table. For example, title is a column in the #__content table that shows the title for each article.

component One type of Joomla extension. Components are normally the main thing on a Joomla page. Core components include com_content (articles in the front end) and com_users (User Manager in the back end). One Joomla page normally contains only one component.

constructor A special (or “magic”) PHP method that is called to create a new object. Invoked with the “new” command (for example, "$reg = new JRestistry()).

controller Part of the model-view-controller (MVC) design pattern used for Joomla core components. The controller executes tasks based on user commands.

cron A Linux program used to schedule command-line (CLI) applications. Can be used in conjunction with Platform CLI applications to automatically run programs on a schedule.

CSS Cascading style sheets. CSS is a style language used to control the appearance of web pages. This can include the layout, fonts, colors, and graphics. Normally, style commands go in separate .css files included with a template.

Data Definition Language (DDL) SQL database query commands that create and change the structure of database tables (for example, CREATE TABLE or ALTER TABLE).

Data Manipulation Language (DDM) SQL database query commands that work with the data inside SQL database tables (for example, SELECT, UPDATE, or DELETE).

data set The data returned by a SQL SELECT query. Contains rows and columns of data.

deprecated method or field A method or field that is planned for removal from the API. Deprecating a method or field puts users of the API on notice that they should change their code so as not to use these parts of the API in future releases.

eclipse An open-source integrated development environment (IDE) that includes a version for working with PHP projects. Used by many Joomla developers.

escaping text A method or function to replace or remove special characters so a string can be safely displayed on a web page. For example, htmlspecialchars() changes the “<” character to “”. This will display in a web page as “<” but will not have the special meaning of opening a tag.

extension In Joomla, an extension is a set of programs that provide a set of functions for the site. Extension types include components, modules, plugins, languages, and templates. Extension can also refer to third-party programs that extend the functionality of the core Joomla package (for example, programs available on the Joomla Extensions Directory at extensions.joomla.org).

FOSS Free and open-source software. Software, like Joomla, that is available for use without charge. FOSS software typically uses a special software license, such as GPL, that requires any derivative works to also be free.

function A set of PHP programming code that does some work. Also known as a method (if it is inside a class). Most Joomla code is inside functions/methods.

GPL General public license. A software license used by Joomla and many other FOSS projects. Available in different versions. Joomla uses GPL2.

hack (core hack) Changing a core Joomla file. This is permitted but not recommended because changes can be lost during updates. In most cases, Joomla can be changed to do a required task without doing core hacks.

hit The number of times a specific page or item is accessed (for example, an article or a banner ad). Joomla tracks hits for many item types.

HTML Hypertext markup language. The language of the web. All web pages are displayed in the browser as HTML text. The browser interprets the HTML code and formats the page accordingly.

HTML5 A new standard for web pages that eventually is expected to replace XHTML. It provides improved processing of audio and video files and is supported by most mobile devices. It is still under development but is expected to become the standard for websites in the future.

IDE Integrated development environment. A set of programs designed to make software developers more productive. For example, IDEs can auto-complete commands, detect syntax errors, debug a program, or allow you to jump to a parent class or method. Examples for PHP include Eclipse and NetBeans.

identical operator In PHP, triple equal signs (“===“). Tests that two values are of the same type (string, integer, etc.) and the same value.

IIS Microsoft Internet Information Services. A web server that runs on Microsoft Windows. Can be used instead of Apache HTTP Server for Joomla.

indexed array Array in PHP stored by numerical order, starting with 0.

INI file File with a “.ini” extension. Used in Joomla to store language files.

JavaScript Programming language that runs inside the client browser, used in many web applications. In Joomla, JavaScript is used to enhance the user interface and provide AJAX functionality.

LAMPP Acronym originally coined from “Linux Apache MySQL Perl/PHP/Python.” Designates the group of programs used to run many dynamic websites. Most Joomla sites run with Apache and MySQL. All run with PHP. In addition, JavaScript is now an important part of the Joomla “stack.”

language pack An installable language extension that provides the option to view a Joomla site in a different language. Language packs can be for the front or back end of the site.

language key The name for a specific piece of language-specific text in a Joomla application. In a Joomla program, language keys are used instead of literal language strings. The actual text is substituted at runtime based on the currently active language.

language override An optional file that allows the site administrator to override any language string in a Joomla site. Two override files are available, one for the front end and one for the administrative back end.

layout override Files that allow you to change the way modules or components are displayed. Override files are placed in special folders and can be used in place of the standard layout files. Unlike Template Overrides, which override layout files of the same name, Layout Overrides are additional layout files.

magic constants Constants in PHP with special meaning. For example, “__FILE__” is always set to the full path of the current PHP file being executed.

magic methods Special methods in PHP that get called automatically. Examples include “__construct()”, which gets called when a new object is created, and “__call()”, which is called whenever a nonexistent method is called.

method Another name for a class function. Often used to refer to functions that are inside a class.

method chaining Using the results of one method to directly call another method. Added to PHP in version 5.

method override A method created in a subclass with the same name as a method in a parent class. If defined, this method is executed instead of the parent method. An override method must have the same method signature as the parent method. A method override can call the parent method with the key word “parent” (for example, "parent::display()").

model One of the three elements of the model-view-controller design pattern. The model typically includes the “business” or “domain” logic and works with the database.

Model-View-Controller (MVC) The design pattern used to create the core components in Joomla A standard OOP design pattern that separates different logical functions into different classes to improve the maintainability of the software.

module A type of Joomla extension. Modules typically are small, simple, and lightweight. A single Joomla page typically contains multiple modules.

MySQL The database used by most Joomla installations and by most dynamic websites in the world.

NetBeans An open-source integrated development environment (IDE) that supports PHP programming.

Object Oriented Programming (OOP) Programming technique based on using classes, objects, and methods. Joomla is based on OOP. OOP is a key advantage of working with Joomla programs.

options (parameters) Options (also known as parameters) are settings that the site administrator can set for a Joomla site that can change the behavior of the site. The core extensions in Joomla offer many options that allow control over many aspects of the site without requiring any programming knowledge.

override See Language Override, Method Override, Alternative Menu Item, Template Override, and Layout Override.

override, template See Template Override.

override, language See Language Override.

override, menu item See Alternative Menu Item.

override, method See Method Override.

override, layout See Layout Override

PHP The programming language that most Joomla code is written in. Also by far the most popular programming language for dynamic websites.

plugin A type of Joomla extension. Plugins are executed at predefined points in the Joomla programming cycle (events) to allow changes to the standard behavior.

plugin event A predefined point in the Joomla execution cycle where a type of plugin is executed.

refactoring Revising a program or set of programs to improve its internal structure without changing its external behavior (the API). For example, reworking the internal workings of a method to improve efficiency while keeping the same method signature and functionality.

router In Joomla, a program that translates between a URL and an array of commands. Normally a router contains two methods, build() and parse(). The build() method takes an array of commands and returns a JURI object. The parse() method reverses this and turns a JURI object into an array of commands.

row A row is part of a database table. One row normally contains the information for one item, such as an article or a user.

slug In Joomla, a value containing the item id and alias for an item, separated by a colon (for example, “123:my-article-alias” or “234:my-category-alias”). Slugs are used to help create SEF URLs

SQL Structured query language. The language used to create SQL queries to work with a SQL database. Includes data-definition language (DDL) and data manipulation language (DML).

template A Joomla extension that controls all aspects of the site’s appearance. The template controls the layout of the pages, as well as the fonts, colors, and graphics.

template override A template override is a layout file that is placed in a special subfolder of the template. If found, it will replace the standard layout file for that template.

ternery operator In PHP, a way to assign a variable based on a true/false condition, with the syntax

$a = ($b == $c) ? $d : $e;

view (MVC) One of the elements of the model-view-controller design pattern used for Joomla core components. The view is responsible for displaying the component in the browser.

view (database) In a SQL database, a saved query that can be used like a table. As of Joomla version 2.5, no views are used in the core database.

web server The program that provides the communication between the browser on the client device and the server where the website files and database are stored. Joomla works with two web servers: Apache and Microsoft IIS.

XHTML Extensible hypertext markup language. A more structured version of HTML that is based on XML. Most Joomla pages are based on XHTML.

XML Extensible markup language. XML files are used in Joomla for installation files, options, and JForm forms.