public function is_off_limit_submission($form_id)
 {
     $submission_limit_per_ip_per_form = (int) $this->get_setting('sub_limit_antispam');
     if ($submission_limit_per_ip_per_form == 0) {
         return false;
     }
     //Calculate starting and ending timestamp for today.
     $N = time();
     $n = 24 * 60 * 60;
     $t = $N % $n;
     $start_ts = $N - $t;
     $end_ts = $start_ts + $n - 1;
     $ip = $this->get_user_ip();
     $res = RM_DBManager::get_generic('STATS', "COUNT(#UID#) AS `count`", "`form_id` = {$form_id} AND `user_ip` = '{$ip}' AND `submitted_on` BETWEEN '{$start_ts}' AND '{$end_ts}'");
     if (!$res) {
         return false;
     }
     // IMP: Do not use '<='. As it counts already done submissions which excludes current submission.
     // If already done submissios are limit-1 then allow this one. Otherwise there will be one extra submission.
     if ((int) $res[0]->count < $submission_limit_per_ip_per_form) {
         return false;
     } else {
         return true;
     }
 }