function costCalc($date,$days,$aid,$adults,$children) {
    if(time("U")> strtotime($date)){
      echo "INVALID DATE";
      return;
    }
    if($days>14||$days<1){
      echo 'INVALID NUMBER OF DAYS';
      return;
    }
    if($adults>10||$adults<1){
      echo 'INVALID NUMBER OF ADULTS';
      return;
    }
    if($children>10||$children<0){
      echo 'INVALID NUMBER OF CHILDREN';
      return;
    }
    if($adults>1){
      $extra=$children*5+($adults-2)*10;
    }
    if($adults==1&&$children<2){
      $extra=0;
    }
    if($adults==1&&$children>1){
      $extra=($children-1)*5+($adults-1)*10;
    }
    switch($aid) {
      case 'US':
        $cost = $days*(35.25+$extra);
        echo number_format((float)$cost, 2, '.', '');
        return;
      case 'PS':
        $cost = $days*(50.25+$extra);
        echo number_format((float)$cost, 2, '.', '');
        return;
      case 'UM':
        $cost = $days*(40.50+$extra);
        echo number_format((float)$cost, 2, '.', '');
        return;
      case 'PM':
        $cost = $days*(60.50+$extra);
        echo number_format((float)$cost, 2, '.', '');
        return;
      case 'C':
        $cost = $days*(100);
        echo number_format((float)$cost, 2, '.', '');
        return;
      default:
        return 'INVALID PRODUCT CODE';

    }
  }