Joomla! Plugin Development

Presentation “Joomla! Plugin Development” - http://slideshare.net/yireo
Jisse Reitsma (jisse@yireo.com) - Twitter @yireo
Joomla! plugin
development

My name is Jisse Reitsma
Developer
Owner of Yireo
Joomla! & Magento
Extensies & development
Tutorials & blogs

Plugins I wrote so far
Language Domains
Auto Login IP
Demo Site
Fancybox
HTTP Authenticatie
New Relic
Piwik
WebP
ScriptMerge
SEF Test
SSL Redirection
Static Content
Trademark
32+ MageBridge plugins
10+ SimpleLists plugins
8+ Dynamic404 plugins

Book release in Autumn 2014
English
About 200-300 pages
Complete reference guide
Available through Amazon
(plus some other channels)

Developing plugins yourself
Part I - Why a plugin?
Part II - A bit of programming
Part III - Hmmm, braindump
Presentation online: http://slideshare.net/yireo
Tweets: @yireo

Part 1:
Why a plugin?

Joomla! extensions
Component
Modules
Plugins
Libraries
Language files

Definition of a Joomla! plugin
A Joomla! extension that offers
functionality based on a triggered event.
The Joomla! core has various core-events
by default, but every Joomla! extension
can trigger additional events.

Plugin-groups (core)
Authentication
Content
System
User
Editors
Editors Xtd
Search
Finder
CAPTCHA
Extension
Quickicon

Plugin-groups (3rd
party)
VirtueMart [product, custom]
JomSocial [community]
K2 [fields]
Yireo
Dynamic404 Match Lookups
SimpleLists Content / Link
MageBridge Product Sales / Newsletter Subscriptions

User-plugin events
onUserLogin
onUserLogout
onUserAuthenticate
onUserLoginFailure
onUserBeforeSave / onUserAfterSave
onUserBeforeDelete / onUserAfterDelete

System-plugin events
onAfterInitialise
onAfterRoute
onAfterDispatch
onBeforeRender / onAfterRender
onBeforeCompileHead

Part 2:
A bit of programming

Reasons for a custom plugin
Modifying HTML-code
Tweaking document-headers
Extending an user-formulier
Extra authentication-type
... and a lot more

System Plugin files
plugins/system/example/example.php
plugins/system/example/example.xml
plugins/system/example/index.html
administrator/languages/en-GB/en-GB.plg_system_example.ini
administrator/languages/en-GB/en-
GB.plg_system_example.sys.ini

Language files (1/2)
PLG_SYSTEM_EXAMPLE="System Example"
PLG_SYSTEM_EXAMPLE_DESC="An example System Plugin"

Language files (2/2)
*.sys.ini = Always loaded
Add plugin title + description, but not much more
*.ini = Only loaded specifically
When editing a plugin in backend
When showing plugin in frontend ($autoLoadLanguage = true)
Add all language strings you need (backend + frontend)

index.html

XML-manifest
<?xml version="1.0" encoding="utf8"?>
<extension version="3.0" type="plugin" group="system">
  <name>PLG_SYSTEM_EXAMPLE</name>
  <description>PLG_SYSTEM_EXAMPLE_DESC</description>
  <version>0.0.1</version>
  <files>
    <filename plugin=”example”>example.php</filename>
    <filename>index.html</filename>
  </files>
  <languages>
    <language tag=”enGB”>enGB.plg_system_example.ini</language>
    <language tag=”enGB”>enGB.plg_system_example.sys.ini</language>
  </languages>
</extension>

System Plugin - basic structure
<?php
defined('_JEXEC') or die();
jimport( 'joomla.plugin.plugin' );
class plgSystemExample extends JPlugin
{
}

System Plugin - hacking HTML
<?php
{
    public function onAfterRender()
    {
        $body = JResponse::getBody();
        // @todo: Do something with the $body
        JResponse::setBody($body);
    }
}

System Plugin - add headers
<?php
{
    public function onAfterDispatch()
    {
        $document = JFactory::getDocument();
        $document>setGenerator('drupal');
        $document>addScriptDeclaration($script);
    }
}

Content Plugin - remove a field
<?php
class plgContentExample extends JPlugin
{
    public function onContentPrepareForm($form, $data)
    {
        $form>removeField('name', 'profile');
        return true;
    }
}

Authenticatie Plugin (1/1)
<?php
class plgAuthenticationExample extends JPlugin
{
  public function onUserAuthenticate($credentials, $options, &$response )
  {
    if ($credentials['password'] == 'joomla') {
      $response>status = JAuthentication::STATUS_SUCCESS;
      $response>error_message = '';
    } else {
      $response>status = JAuthentication::STATUS_FAILURE;
      $response>error_message = JText::_('JGLOBAL_AUTH_INVALID_PASS')
    }
  }
}

Part 3:
Braindump

Calling a content-event [1/2]
Scenario: Own component is offering content-object ($item)
Purpose is to modify the $item title through extra plugins
Use of content-event onContentContent
All $item-properties can be modified through this event
Dispatch event in component-view
For example in views/item/view.html.php

Calling a content-event [2/2]
JPluginHelper::importPlugin( 'content' );
$dispatcher = JDispatcher::getInstance();
$arguments = array(&$item, &$item_params, 0);
$results = $dispatcher>trigger(
'onPrepareContent', $arguments
);
Note $item is a PHP reference (ampersand &).
Return-variabele $results contains at most an event-status.

Calling your own event (1/3)
Create a custom component
components/com_example
Create a custom plugin-group
plugins/custom
Create a custom plugin
plugins/custom/example/example.php
plugins/custom/example/example.xml
plugins/custom/example/index.html

class plgCustomExample extends JPlugin
{
    public function doSomething()
    {
        // @todo: Do something
    }
}

Add this to the right place in your MVC-component:
JPluginHelper::importPlugin('custom');
$dispatcher = JDispatcher::getInstance();
$arguments = null;
$results = $dispatcher>trigger(
'doSomething', $arguments
);

Checks (1/2)
Handy variables:
$app = JFactory::getApplication();
$document = JFactory::getDocument();
Check whether the current application is the frontend:
if(!JFactory::getApplication()>isSite()) return false;
Check whether the current output is an HTML document:
if (JFactory::getDocument()>getType() != 'html')
return false;

Checks (2/2)
Ignore AJAX-requests:
$input = JFactory::getApplication()>input;
if ($input>getCmd('tmpl') == 'component') return false;
if ($input>getCmd('format') == 'raw') return false;
if (isset($_SERVER['HTTP_X_REQUESTED_WITH']) &&
strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) ==
'xmlhttprequest') return false;

Parameters in J1.5 vs J2.5
private function getParams()
{
  jimport('joomla.version');
  $version = new JVersion();
  if(version_compare($version>RELEASE, '1.5', 'eq')) {
    $plugin = JPluginHelper::getPlugin('system','example');
    $params = new JParameter($plugin>params);
    return $params;
  } else {
    return $this>params;
  }
}

Loading a language file - Joomla! 2.5
public function __construct(& $subject, $config)
{
parent::__construct($subject, $config);
$this>loadLanguage();
}

Loading a language file - Joomla! 3.x
protected $autoloadLanguage = true;

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