Introduction

Requirements

• Joomla 1.0 or greater

Let's Roll

The Event Handler

<?php
/**
* @version 4.5.2
* @package HelloWorld
* @copyright (C) 2005 Andrew Eddie
* @license http://www.gnu.org/copyleft/gpl.html GNU/GPL
*/
 
/** ensure this file is being included by a parent file */
defined( '_VALID_MOS' ) or
    die( 'Direct Access to this location is not allowed.' );
 
// include support libraries
require_once( $mainframe->getPath( 'admin_html' ) );
 
// handle the task
$task = mosGetParam( $_REQUEST, 'task', '' );
 
switch ($task) {
    default:
        helloScreens::helloWorld();
        break;
}
?>

• The comment block at the top of the file defines meta data about the file, in particular the license and the copyright.  This block has some special notations that are able to be parsed by an application called phpDocumentor.  It is used to assemble API (Application Programmer Interface) documentation.  The important thing here is to have a version and explicitly state the copyright and license terms for the file.
• Next we look for a constant called _VALID_MOS.  Because this constant is defined elsewhere in Joomla, it ensures that only Joomla is trying to access this file.  It prevents a user from opening the file explicitly in a browser.
• We then include the file that will support the presentation layer.  $mainframe is a global variable in Joomla that has lots of useful methods attached to it.  One of these methods is getPath.  It helps you find common types of files.  In this instance we want the admin.hello.html.php file to be include, so we pass 'admin_html' to the getPath method.
• Next we determine what task has been passed through the URL.  To do this we use a utility function in Joomla called mosGetParam.  It takes three arguments, a source array, a key in the array to search for and a default value to assign if that key is not found.  In most instances we are not sure if the task is going to come through the URL or a form post, so we use $_REQUEST as the source array.
• We then pass the task to a switch control structure.  We only have one thing to do in this example so it doesn't much matter if a task has been nominated or not.  Whatever the case, we are going to call a static class method called helloScreens::helloWorld.
  

Preparing for Output

<?php
/**
* @version 4.5.2
* @package HelloWorld
* @copyright (C) 2005 Andrew Eddie
* @license http://www.gnu.org/copyleft/gpl.html GNU/GPL
*/
 
/** ensure this file is being included by a parent file */
defined( '_VALID_MOS' ) or
    die( 'Direct Access to this location is not allowed.' );
 
/**
 * @package HelloWorld
 */
class helloScreens {
    /**
     * Static method to create the template object
     * @return patTemplate
     */
    function &createTemplate() {
        global $option, $mosConfig_absolute_path;
        require_once( $mosConfig_absolute_path
            . '/includes/patTemplate/patTemplate.php' );
 
        $tmpl =& patFactory::createTemplate( $option, true, false );
        $tmpl->setRoot( dirname( __FILE__ ) . '/tmpl' );
 
        return $tmpl;
    }
    /**
     * A simple message
     */
    function helloWorld() {
        // import the body of the page
        $tmpl =& helloScreens::createTemplate();
        $tmpl->setAttribute( 'body', 'src', 'helloworld.html' );
 
        $tmpl->displayParsedTemplate( 'form' );
    }
}
?>

The HTML Output File

<mos:comment>
@version 4.5.2
@package HelloWorld
@copyright (C) 2005 Andrew Eddie
@license http://www.gnu.org/copyleft/gpl.html GNU/GPL
</mos:comment>
 
<h1>Hello World<h1>