Where to put my function?

[crushisai]

I've created this funciton :

 

static protected $cacheName = array();
public static function getCmsNameById($id_cms_category)
{
if (!isset(self::$cacheName[$id_cms_category]))
self::$cacheName[$id_cms_category] = Db::getInstance(_PS_USE_SQL_SLAVE_)->getValue('
SELECT `name`
FROM `'._DB_PREFIX_.'cms_category_lang`
WHERE `id_cms_category` = '.(int)$id_cms_category.'
'
);


return self::$cacheName[$id_cms_category];
}

as you can see its just a copy from getNameById in manufacturer.php just with it being adapted to display cmscategory name with a given ID. 

The issue I have is I dont know where to put this code, if I put it in link.php Im able to retrieve the information via

{$link->getCmsNameById(2)}

but Im pretty sure thats not the right way to do it.. I tried placing my code in CMS.php and also CMSCategory.php with no success, 

 

I've tried to look on the documentation but Im not able to find whats the correct way.

 

If you can help me understand the system better or pointing me where to read would be awesome. 

Thanks in advance