Logically select categories and subcategories (php,joomla,javascript,ajax)

You can use below query for get categories.

 function all_cat($id='',$child_of_child='parent')    {            $CI =& get_instance();            if($id="")            {                $query = $CI->db->get_where("__jbusinessdirectory_categories",array('parent_id'=>1));            }            else            {                 $query = $CI->db->get_where("__jbusinessdirectory_categories",array('parent_id'=>$id));            }               //echo $CI->db->last_query()."<br>";            $op = '';            if($query->num_rows() > 0)            {                $res = $query->result();                //pr($res);                if($child_of_child == 'child')                {                    $op .= '<ul class="sub_cat  mrg-top-5" style="display:none;" id="'.$id.'">';                }                else                {                    $op .= '<ul class="sub_cat " id="'.$id.'">';                }                foreach($res as $r)                {                    $op .= '<li><a href="'.site_url('category/search/9/1V1/'.$r->id).'" class="temp">'.ucwords($r->name).'</a>                            </li>';                    $op .= all_cat($r->id,$child_of_child='child');                }                   return $op .= '</ul>';            }            else            {                return $op;            }    }

It appears that the code already does what you want. You want 2 queries and there are 2. But, I think the result of these 2 queries combines into 1 result and you want to keep it spit into 2 results.

You will have to add new category functions that accept category ID parameters.

<?phpstatic function getCategoryById($id){  $id = intval( $id );   $db = JFactory::getDBO();  $query = '       SELECT *        FROM #__jbusinessdirectory_categories       WHERE              published=1         AND id= '.$id;  $db->setQuery($query);  return $db->loadObject();}static function getChildCategoryList($id){  $id = intval($id);  $db = JFactory::getDBO();  $query = '       SELECT c.*       FROM #__jbusinessdirectory_categories c       INNER JOIN  #__jbusinessdirectory_categories  cc         ON c.parent_id = cc.id       WHERE c.parent_id!=1       AND cc.id = '.$id.'       AND c.published=1       ORDER BY c.name';     $db->setQuery($query,0,1000);     $result = $db->loadObjectList();     return $result;}

I am not familiar with Joomla code that retrieves parameters but you can find the ID if you POST it when someone selects a main category.

<?phpif($params->get('showCategories')){    $categoryId = (int) $params->get('mainCategory');    $category   =  modJBusinessDirectoryHelper::getCategoriesById($categoryId);    $subCategories = modJBusinessDirectoryHelper::getChildCategoryList($categoryId);    }}