//일주일/ 14일전 날짜 구하기
  $old_cul_date = date('Y-m-d',strtotime('-14 day'));
  $cul_date = date('Y-m-d',strtotime('-7 day'));
  $today = date('Y-m-d');

  $sql = "select * from $t_board"."_$id where is_secret=0 and (date_format('Y-m-d',reg_date) > $old_cul_date) and (date_format('Y-m-d',reg_date) < $cul_date) order by rand() limit $num";