Joomla: Read custom article parameters from a module

In implementing a web site on Joomla, I came across a common issue: I needed to pass additional parameters with an article into a 3rd-party module. In this case, the module was the Joomla AnythingSlider, a very slick and flexible content slider/carousel.

The initial task of creating the custom parameters wasn't so bad; the first thread in this post covers that. You add the parameter to the advanced section of the file administrator/components/com_content/models/article.xml:

<param name="article_type" type="radio" default="default" 
     label="Article Type" description="article type">
  <option value="default">Default</option>
  <option value="picture">Picture (rotator)</option>
  <option value="video">Video (rotator)</option>
</param>

However, reading the values in a module is a different story. Here's the syntax to fetch all the parameters from article.xml:

$paramsdefs = JPATH_COMPONENT.DS.'models'.DS.'article.xml';
$myparams = new JParameter( $paramsdata, $paramsdefs );

And here's how a specific custom parameter is read (in this case, it's called article_type):

echo "Article type: ". $myparams->get('article_type');

This is thanks to another reply to the same post on the Joomla forums, but page 2.

UPDATE: A good quested was raised about one of the variables used in the above code: $paramdata. Where was it defined? Well, it's not in the above code, but in the AnythingSlider Joomla extension, mod_anythingslider; you can download it from here.

The mod_anythingslider has a helper.php file, which defines the class ModSlideShow:

<?php
/**
 * AnythingSlider Helper Classes
 * 
 * @package    Joomla 1.5.0
 * @subpackage Modules
 * @Copyright  Copyright (c)2010 Dnote Software
 * @license    GNU/GPL, see http://www.gnu.org/copyleft/gpl.html
 *
 * mod_anythingslider is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * Parts of this software are based on AnythingSlider By Chris Coyier: http://css-tricks.com
 **/

 defined('_JEXEC') or die('Direct Access to this location is not allowed.');
 
class ModSlideShow
{
    /**
     * Returns a list of articles
    */
    function getSlideshow(&$params, &$access)
 {
  global $mainframe;

  $db  =& JFactory::getDBO();
  $user  =& JFactory::getUser();
  $aid = $user->get('aid', 0);

  $catid  = (int) $params->get('catid', 0);
  $items  = (int) $params->get('items', 0);

  $contentConfig = &JComponentHelper::getParams( 'com_content' );
  $noauth   = !$contentConfig->get('show_noauth');
  $date =& JFactory::getDate();
  $now = $date->toMySQL();

  $nullDate = $db->getNullDate();
  
  // Ordering
  switch ($params->get( 'ordering' ))
  {
   case 'o_asc':
    $ordering  = 'a.ordering';
    break;
   case 'o_dsc':
    $ordering  = 'a.ordering DESC';
    break;
   case 'm_dsc':
    $ordering  = 'a.modified DESC, a.created DESC';
    break;
   case 'c_dsc':
   default:
    $ordering  = 'a.created DESC';
    break;
  }

  // query to determine article count
  $query = 'SELECT a.*,' .
   ' CASE WHEN CHAR_LENGTH(a.alias) THEN CONCAT_WS(":", a.id, a.alias) ELSE a.id END as slug,'.
   ' CASE WHEN CHAR_LENGTH(cc.alias) THEN CONCAT_WS(":", cc.id, cc.alias) ELSE cc.id END as catslug'.
   ' FROM #__content AS a' .
   ' INNER JOIN #__categories AS cc ON cc.id = a.catid' .
   ' INNER JOIN #__sections AS s ON s.id = a.sectionid' .
   ' WHERE a.state = 1 ' .
   ($noauth ? ' AND a.access <= ' .(int) $aid. ' AND cc.access <= ' .(int) $aid. ' AND s.access <= ' .(int) $aid : '').
   ' AND (a.publish_up = '.$db->Quote($nullDate).' OR a.publish_up <= '.$db->Quote($now).' ) ' .
   ' AND (a.publish_down = '.$db->Quote($nullDate).' OR a.publish_down >= '.$db->Quote($now).' )' .
   ' AND cc.id = '. (int) $catid .
   ' AND cc.section = s.id' .
   ' AND cc.published = 1' .
   ' AND s.published = 1' .
   ' ORDER BY '.$ordering ;
  $db->setQuery($query, 0, $items);
  $rows = $db->loadObjectList();

  return $rows;
 }
 
}
?>

Then in the mod_anythingslider.php, we define a few more variables:

$params->set('intro_only', 1);
$params->set('hide_author', 1);
$params->set('hide_createdate', 0);
$params->set('hide_modifydate', 1);

// Disable edit ability icon
$access = new stdClass();
$access->canEdit = 0;
$access->canEditOwn = 0;
$access->canPublish = 0;
// Other code here...
$slideShow = ModSlideShow::getSlideshow($params, $access);

Now we bring it all together in the default.php, which generates the HTML for the slider:

/* 
  Variables used throughout the main foreach loop. 
  Don't define these in the loop b/c they'll get
  created for each article in the carousel.
*/
$paramsdefs = JPATH_COMPONENT.DS.'models'.DS.'article.xml';
$limitstart = JRequest::getVar('limitstart', 0, '', 'int');
$dispatcher =& JDispatcher::getInstance();

/*
  Main foreach loop of the carousel component. Runs
  once for each article in the slideshow.
*/
foreach ($slideShow as $item){ 
  echo "<li>"; 
  $aparams =& $item->parameters;
  $params->merge($aparams);
  
  $item->text = $item->introtext;
  $results = $dispatcher->trigger('onPrepareContent', array (& $item, & $params, $limitstart));
  
  $paramsdata = $item->attribs;
  $myparams = new JParameter( $paramsdata, $paramsdefs );
  $article_type = $myparams->get('article_type');
  // More processing inside the foreach...
}

Hope this helps those confused by the $paramdata variable.