Joomla 2.5 Parent Category ID

Question

I'm trying to get the id of the parent category of another category. (I have the ID of the child Category.)

I've been trying to use Joomla's Category model, I successfully used the Article equivalent to get the Child Category ID from the Id of an article.

//article model
jimport('joomla.application.component.model');
$articlesModel = JModel::getInstance('ContentModelArticle');
$categoriesModel = JModel::getInstance('ContentModelCategory');

//Get Article Category id
$article = $articlesModel->getItem($art['id']);
$catid = $article->catid;

//Get Category Parent Category
$category = $categoriesModel->getItem($catid);
$parentID = $category->getParent();

echo "<pre>";
var_dump($parentID);
echo "</pre>";

But I keep getting an error saying that I'm trying to call a function of a non-object.

Can someone point out where I'm going wrong please? Thanks.

Edit: Should have mentioned this is all within the module file

Changed Tactic I found a different way to do this myself in the end: Now I'm querying the database for the information. It's useful in this case because I can grab the exact data I need.

$db =& JFactory::getDBO();
$query = $db->getQuery(true);
$query->select('parent_id');
$query->from('#__categories'); 
$query->where("id = '$child_id'");    
$db->setQuery($query);

//check if error
if ($db->getErrorNum()) {
  echo $db->getErrorMsg();
  exit;
}
$parent = $db->loadObjectList();
$parent_id = $parent['0']->parent_id;

Answer 1

If you want to load the ContentModelCategory, you better use prefixing:

$categoriesModel = JModel::getInstance('Category','ContentModel');

However, I don't believe that this is the right model for you, as it gets its context from the request.

I can suggest 2 alternatives:

Use a JCategories instance

This is the preferred method, used by the content component.

$article = $articlesModel->getItem($id);
$catid = $article->catid;

//Get Category Parent Category
$categoriesModel = JCategories::getInstance('content');
$category = $categoriesModel->get($catid);
$parent = $category->getParent();
if($parent){
    $parentId = $parent->id;
    echo "parentId: ".$parentId;
}

Use a CategoriesModelCategory

This is the model used by com_categories.

$article = $articlesModel->getItem(5);
$catid = $article->catid;

//add the CategoriesModelCategory model include path 
JModel::addIncludePath (JPATH_ADMINISTRATOR . DS . 'components' . DS . 'com_categories' . DS . 'models');
//add the table include path required by the model
JTable::addIncludePath (JPATH_ADMINISTRATOR . DS . 'components' . DS . 'com_categories' . DS . 'tables');

$categoriesModel = JModel::getInstance('Category','CategoriesModel');
$category = $categoriesModel->getItem($catid);
if($category){
    $parentId = $category->parent_id;
    echo "parentId: ".$parentId;
}