How to remove duplicate rows from stdClass codeigniter

    stdClass Object
    (
        [id] => 132
        [slug] => test
        [parent_id] => 15
    )
    stdClass Object
    (
        [id] => 132
        [slug] => test
        [parent_id] => 15
    )

I used the array_unique function to delete duplicate data, but it gave the following error

Message: array_unique() expects parameter 1 to be array, object given

here is my code:

  > //get category
//build category query
public function build_query($lang_id = null)
{
    if (empty($lang_id)) {
        $lang_id = $this->selected_lang->id;
    }
    $ci =& get_instance();
    if (item_count($ci->languages) > 1) {
        return "SELECT categories.*, categories.parent_id AS join_parent_id, categories_lang.name AS name,
            (SELECT slug FROM categories WHERE id = join_parent_id) AS parent_slug,
            (SELECT name FROM categories_lang WHERE categories_lang.category_id = categories.id AND categories_lang.lang_id != " . $this->db->escape(clean_number($lang_id)) . "  ORDER BY categories_lang.lang_id LIMIT 1) AS second_name
            FROM categories
            LEFT JOIN categories_lang ON categories.id = categories_lang.category_id AND categories_lang.lang_id = " . $this->db->escape(clean_number($lang_id)) . " ";
    } else {
        return "SELECT categories.*, categories.parent_id AS join_parent_id, categories_lang.name AS name,
            (SELECT slug FROM categories WHERE id = join_parent_id) AS parent_slug
            FROM categories
            LEFT JOIN categories_lang ON categories.id = categories_lang.category_id AND categories_lang.lang_id = " . $this->db->escape(clean_number($lang_id)) . " ";
    }
}
    >     public function get_category($id)
    >     {
    >         $sql = $this->build_query() . "WHERE categories.id = ?";
    >         $query = $this->db->query($sql, array(clean_number($id)));
    >         return $query->row();
    >     }
    > 
    >  function get_category_by_id($id)
    >     {
    >         $ci =& get_instance();
    >         return $ci->category_model->get_category($id);
    >     }
 $item_category = get_category_by_id($product->category_id);
    > 
    >  print_r(array_unique($item_category));