1. Add a check box at the bottom of the first page that is labeled Compound Interest Monthly. If this box is checked, the interest should be calculated monthly instead of yearly, so you need to change the Future Value calculation to provide for that.

2. On the second page, display some text that indicates whether the interest is being calculated monthly or yearly.

3. Code to calculate compounding monthly is in the image below.

4. Below is an example of the page when loaded.

5. And, if the Compound Interest Monthly checkbox is checked, this would be the result

display_results.php -

// validate investment if ($investment === FALSE ) { $error_message = 'Investment must be a valid number.'; } else if ( $investment

} else if ( $interest_rate >= 15 ) { $error_message = 'Interest rate must be less than or equal to 15.'; // validate years

} else if ( $years === FALSE ) { $error_message = 'Years must be a valid whole number.'; } else if ( $years 30 ) { $error_message = 'Years must be less than 31.'; // set error message to empty string if no invalid entries } else { $error_message = ''; }

// if an error message exists, go to the index page if ($error_message != '') { include('index.php'); exit(); }

// calculate the future value $future_value = $investment; for ($i = 1; $i

// apply currency and percent formatting $investment_f = '$'.number_format($investment, 2); $yearly_rate_f = $interest_rate.'%'; $future_value_f = '$'.number_format($future_value, 2);

$now = new DateTime();

?>

Future Value Calculator

Investment Amount:

Yearly Interest Rate:

Number of Years:

Future Value:

This calculation was done on: format('m-d-Y'); ?>

index.php -

Future Value Calculator

Investment Amount:

Yearly Interest Rate:

Number of Years:

if (isset (S_POSTI' compound monthly'])) 7compound monthly compounded_monthly -'Yes' Smonths?years12; Smonthly_rate - s / 12: for ($i-1: $i