<?php
  $amount_paid = 65.50;
  $totaldays = date('t',strtotime('15-02-2019'));
  $amount_paid_per_day = $amount_paid/$totaldays;
  $start_date = date('d',strtotime('15-02-2019'));
  $today_date = date('d');
  $total_refund_day = $totaldays -($today_date - $start_date);
  $total_refund_amount = number_format($amount_paid_per_day*$total_refund_day,2,'.','');
  echo $totaldays.'--total days in month specified--'.$amount_paid.' ----- '. $total_refund_day .' ---- '.$total_refund_amount;

?>