PHP 8 fatal: undefined $categoryOptions in Falang filter

-- HikaShop version -- : 6.6.0_2026-09-08_05-07-16
-- Joomla version -- : 6.1.3
-- PHP version -- : 8.5.9

Hello,

I would like to report a small issue in the Falang content element file
shipped with HikaShop.

File:
back/falang/translationHikashop_product_categoryFilter.php
(installed to administrator/components/com_falang/contentelements/)
Version: 6.6.0, package downloaded 2026-09-08

In _createfilterHTML(), the variable $categoryOptions is only assigned
inside the foreach loop:

$category_list = $db->loadObjectList();
foreach($category_list as $k=>$category){
$categoryOptions[$k] = \Joomla\CMS\HTML\HTMLHelper::_('select.option', ...);
}
...
$options = array_merge($allCategoryOptions, $categoryOptions);

It is never initialized before the loop. If the query returns no rows,
$categoryOptions stays undefined and is passed to array_merge(). On PHP 8
this is a fatal error:

array_merge(): Argument #2 ($arrays) must be of type array, null given

The query only returns rows when at least one product is linked to a
category, so the empty result happens when the shop has no products yet,
or when no product is assigned to any category.

Suggested fix, one line before the loop:

$categoryOptions = array();

How this was found, and what it is not:

I updated Falang Pro from 6.8 to 6.9 and asked Claude (an AI assistant) to
compare the affected files so I would know which of my manual patches had
to be reapplied. During that review it noticed this uninitialized variable
and recommended that I report it to you. I then downloaded the current
HikaShop Business package on 2026-09-08 and confirmed the code is still
unchanged in 6.6.0.

So this is a code review remark, not a reproduced bug. I have not seen the
error on my own site: all of my products are assigned to categories, so
the query is never empty here. Please weigh it accordingly.

My environment:
Joomla 6.1 / PHP 8 / HikaShop Business 6.6.0 / Falang Pro 6.9

By the way, thank you for switching this file from JFactory / JHtml / JText
to the namespaced classes in 6.6.0. I had been patching it by hand for
Joomla 6, and that is no longer necessary.

Best regards,