在最新版本的localhost中通过引用传递的不推荐错误

All the project is error free on localhost vertrigo_222 (and also on livehost).
Now I am trying to upgrade my localhost to latest version vertrigo_230.
I am facing following deprecated error:

Here is line number 1170 and 1171:

calculate_city_row_col($row['attacker_city_id'], &$att_city_row, &$att_city_col);
calculate_city_row_col($row['defender_city_id'], &$def_city_row, &$def_city_col);

Please give me some solution.
Thank you in advance.

I think you can try remove & before $att_city_row and $att_city_col, $def_city_row, $def_city_col