Creating an Extension: Outline

This is intended to be a cheatsheet, of the steps to follow when making an extension (component, module, or plug-in) for Joomla.

it is following the LeBlanc book, making a component for restaurant reviews. So the naming scheme is using the word "reviews". In your own extension, of course replace with your component name.

It is a summary of the process explained in Chapter 12 of Learning Joomla Extension Development, by Joseph LeBlanc, Packt Publishing, 2007.
With some information added from Mastering Joomla 1.5 Extension and Framework Development, James Kennard, Packt Publishing, 2007.

The outline

Start it: Getting Started with Component Development Chapter 2, page ?

Making the structure: Before you begin with coding, there are a few files and folders that have to be created, and also a query that has to be run. Then you create a menu item and admin toolbars to access your component – At this point, your component won't actually do anything yet!

Create component folders:
- /components/com_reviews
- /components/administrator/com_reviews
Create component base files (empty for now):
- /components/com_reviews/reviews.php
- /administrator/components/com_reviews/admin.reviews.php
Executing the Component (pp 12-14)
Add code to the two php files:

Load the component's front end:
http://jmltry/index.php?option=com_reviews
nothing there in content!

open reviews.php and add:

    <?php
    defined( '_JEXEC' ) or die( 'Restricted access' );
    echo '<div class="componentheading">Restaurant Reviews</div>';
    ?>

Now make it available in admin. Put in admin.reviews.php:

    <?php
    defined( '_JEXEC' ) or die( 'Restricted access' );
    echo 'Restaurant Reviews';
    ?>

check it:
http://jmltry/administrator/index.php?option=com_reviews

Mysql prompt:

    INSERT INTO jos_components (name, link, admin_menu_link,
            admin_menu_alt, `option`, admin_menu_img, params)
    VALUES ('Restaurant Reviews', 'option=com_reviews',
        'option=com_reviews', 'Manage Reviews', 'com_reviews',
        'js/ThemeOffice/component.png', '');

OR
PHPMyAdmin or other GUI:
Insert the values into corresponding fields in jos_components table.

Leave all of the other fields blank. The fields menuid, parent, ordering, and iscore will default to 0, while enabled will default to 1.
What this does:
gives the system some basic information about your component.
(It is not necessary to add this query while developing the component; once you create the basic directories and files, your component is ready to be executed.)
- States the name you want to use for the component (can contain spaces and punctuation).
- You can put in specific links to go to both the front end and back end.
- Defines the image to be used on the Components menu.
- Description in the browser status bar can be made available.
- Adds a menu item in the back end
- Makes it possible to add an appropriate link in the front end without hard-coding a URL.

Now that component is registered, you can create a menu link: (pp. 16-18)
- Go to Menus | Main Menu and click New.
- From this screen, "Restaurant Reviews" will now appear in the list of nodes.
- Select it, and enter "Reviews" as the Name.
- Save, and go reload the front end – there will be a "Reviews" link in the main menu, which will go to Reviews page.
Creating Toolbars (pp. 18-21)

Create the toolbar.reviews.html.php file in the administrator/components/com_reviews folder, with:

    <?php
    defined( '_JEXEC' ) or die( 'Restricted access' );
    class TOOLBAR_reviews {
        function _NEW() {
            JToolBarHelper::save();
            JToolBarHelper::apply();
            JToolBarHelper::cancel();
        }
        function _DEFAULT() {
            JToolBarHelper::title( JText::_( 'Restaurant Reviews' ),
                                            'generic.png' );
            JToolBarHelper::publishList();
            JToolBarHelper::unpublishList();
            JToolBarHelper::editList();
            JToolBarHelper::deleteList();
            JToolBarHelper::addNew();
        }
    }
    ?>

The class JToolBarHelper contains functions that generate all the HTML necessary to build toolbars.
You can also add custom HTML output from within these functions.
(Be aware that the toolbars lie within HTML tables; you will probably want to add tags along with your custom navigation.)

Create the toolbar.reviews.php file in the administrator/components/com_reviews folder, with:
```
    <?php
      defined( '_JEXEC' ) or die( 'Restricted access' );
      require_once( JApplicationHelper::getPath( 'toolbar_html' ) );
      switch($task) {
        case 'edit':
        case 'add':
            TOOLBAR_reviews::_NEW();
            break;
        default:
            TOOLBAR_reviews::_DEFAULT();
            break;
      }
    ?>
```
- The call to getPath() allows you to call up the toolbar.reviews.html.php file without committing to a component name. Later, even if you change the name to 'Restaurants' and also change the filenames, this line of code will still load the output code for the toolbar with no modification.
- To see the toolbars, refresh the browser in the back end and go to Components → Restaurant Reviews.
- To see the other toolbar, add &task=add to the end of the URL in your browser, and load it.
  This second toolbar will work from "Add" button after we build the forms in the back end.
- The book (p. 21) shows all available buttons and associated commands.

The Back-end Back-End Development Chapter 3, page 22

Creating the Database Table
Creating a Table Class
Creating the Review Form
Processing the Data
Creating a List Screen
Editing Records
Deleting Records

The Front-end: Front-End Development Chapter 4, page xx

Listing the Reviews
Displaying a Review
Generating Search-Engine Friendly Links
Building URL Segments
Parsing URL Segments
Adding Comments
Displaying Comments

The Module code: Module Development Chapter 5, page xx

Registering the Module in the Database
Creating and Configuring a Basic Module
Recruiting Some Helpers
Try Some Different Layouts
Mixing it Up

Expanding it Expanding the Project Chapter 6, page xx

Model, View, Controller: Why?
Building Data Models
Modeling All Reviews
Modeling Individual Reviews
Migrating to Views
Viewing All
Viewing One
Switching Through Controllers
Updating Links and Routes
Reorganizing the Back-End Code
Publishing Controls for Reviews
Adding Pagination
Management for Comments
Additional Toolbars

Plug-in Behind the Scenes: Plug-Ins Chapter 7, page xx

Database Queries
A Simple Link Plug-In
An Information Box Plug-In
Searching the Reviews

Configuring Configuration Settings Chapter 8, page xx

Adding Parameters to Extensions
Parameters for Modules
Parameters for Plug-Ins
Parameters for Components

Packing it up Packing Everything Together Chapter 9, page xx

Listing All Files
Packaging the Module
Packaging Plug-ins
Packaging the Component
Including SQL Queries
Creating Back-End Menu Items
Extra Installation Scripts
Distribution

Useful tools for writing Joomla code

J!Dump for debugging
http://joomlacode.org/gf/project/jdump
- Output is displayed in a configurable pop-up window.
  Describes data types, and object properties and methods.
- Comes as a component and a system plugin. Need to install both.
- To output variables:
```
    // create example object
    $object = new JObject();
    $object->set('name', 'example');
    // dump object to popup
    dump($object, 'Example Object'); 
```
- Other functions are dumpMessage(), dumpSysinfo(), dumpTemplate(), and dumpTrace().
Jdocumentor — Document your code (Chapter 2, Mastering book)

Details of component development From Mastering Joomla 1.5 Extensions

How it works: How the Joomla app works; PHP in Joomla; multi-language support; unicode handling; good coding practice; how to document your code;; Mastering Joomla 1.5 Extensions, Chapter 2.
Using database in Joomla extension: Table structure, Joomla functions to access database, joins etc.; Mastering Joomla 1.5 Extensions, Chapter 3.
Designing a component: Concepts, Model-View-Controller (MVC), coding your component, configuration for the component, router for SEO urls, packaging, installing.; Use Joomla Web Links component as an example.; Mastering Joomla 1.5 Extensions, Chapter 4.
Designing a Module: Setting up a sandbox, settings, helpers, layouts, translating, packaging.; Mastering Joomla 1.5 Extensions, Chapter 5.
Designing a Plugin: Setting up a sandbox, events, listeners, groups, loading, as libraries, translating, settings, packaging, file naming.; Mastering Joomla 1.5 Extensions, Chapter 6.
General Extension Design: Classes, helpers, instances, JRegistry, user, session, browser, assets.; Mastering Joomla 1.5 Extensions, Chapter 7.
Rendering Output: Using joomla.html library, building templates, making component back-end,; Mastering Joomla 1.5 Extensions, Chapter 8.
Customizing the page: Custom messages, redirects, customizing the back end, modifying "the document" (title, breadcrumbs, stylesheet and javascript calls, translating, tooltips, etc.),; Mastering Joomla 1.5 Extensions, Chapter 9.
APIs and Web Services: XML, AJAX, LDAP, Email, FTP, using web services APIs.; Mastering Joomla 1.5 Extensions, Chapter 10.
Error-handling and Security: errors/warnings/notices, cgi requests, access control, handling attacks.; Mastering Joomla 1.5 Extensions, Chapter 11.
Utilities and Useful Classes: JArchive, JArrayHelper, JDate, JFile, JFolder, JLog, JMail, JNode, JPath, JTree; Mastering Joomla 1.5 Extensions, Chapter 12.
Joomla Classes, Parameters, and Configuration reference: Mastering Joomla 1.5 Extensions, Appendix

Know more

The sources: These two books are excellent. From them, you will learn not only how to make extensions for Joomla, but lots about programming in general.; Learning Joomla Extension Development, by Joseph LeBlanc, Packt Publishing, 2007.
jlleblanc.com; Mastering Joomla 1.5 Extension and Framework Development, James Kennard, Packt Publishing, 2007.
webamoeba.co.uk; These are for sale as paper books and as PDF at PacktPub.com, or contact James.
General info:: www.tibetangeeks.com/technologies/web_development/cms/; General info and howtos for Wordpress, Joomla, and Drupal.

All content not copyright by anyone else is copyright © 2003–2009 James Walker.
License for use is the GNU Free Documentation License. Find it:
here in the License directory
or at the Free Software Foundation, www.fsf.org