#magento - get previous/next #category

Navigation.php

<?php
/**
 * Additional Methods for Mage Core Navigation
 *
 * @category    Scandi
 * @package     Scandi_Extends
 */
class Scandi_Extends_Block_Catalog_Navigation extends Mage_Catalog_Block_Navigation
{
    private function getCategoryByPositionOffset($offset)
    {
        $currentCategory = Mage::registry('current_category');

        if ($currentCategory) {
            // Get Parent category subCategories
            $categories = Mage::getModel('catalog/category')->load($currentCategory->parent_id)->getChildrenCategories();

            if (count($categories) > 0) {
                // Create subCategories Id's array
                $categoryPosIdArr = array();
                foreach ($categories as $category) {
                    array_push($categoryPosIdArr, (int)$category->getId());
                }

                $categoryPos = array_search($currentCategory->getId(), $categoryPosIdArr) + $offset;

                if (isset($categoryPosIdArr[$categoryPos])) {
                    $categoryId = $categoryPosIdArr[$categoryPos];

                    return Mage::getModel('catalog/category')->load($categoryId);
                }
            }
            return false;
        }
        return false;
    }

    public function getNextCategory()
    {
        return $this->getCategoryByPositionOffset(1);
    }

    public function getPreviousCategory()
    {
        return $this->getCategoryByPositionOffset(-1);
    }
}

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