Modify the Future Value Application so it uses a persistent session to save the last values entered by the user for 2 weeks.

display_results.php

// get the data from the form

$investment = filter_input(INPUT_POST, 'investment',

FILTER_VALIDATE_FLOAT);

$interest_rate = filter_input(INPUT_POST, 'interest_rate',

FILTER_VALIDATE_FLOAT);

$years = filter_input(INPUT_POST, 'years',

FILTER_VALIDATE_INT);

// validate investment

if ($investment === FALSE ) {

$error_message = 'Investment must be a valid number.';

} else if ( $investment

$error_message = 'Investment must be greater than zero.';

// validate interest rate

} else if ( $interest_rate === FALSE ) {

$error_message = 'Interest rate must be a valid number.';

} else if ( $interest_rate

$error_message = 'Interest rate must be greater than one.';

} 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

$error_message = 'Years must be greater than zero.';

} 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

$future_value =

$future_value + ($future_value * $interest_rate * .01);

}

// 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

//set default value of variables for initial page load

if (!isset($investment)) { $investment = ''; }

if (!isset($interest_rate)) { $interest_rate = ''; }

if (!isset($years)) { $years = ''; }

?>

Future Value Calculator

Investment Amount:

value="">

Yearly Interest Rate:

value="">

Number of Years:

value="">

Future Value Calculator Investment Amount Yearly Interest Rate: Nurmlpr of Years Future Value: $1,000.00 5% $1,276.28 This calculation was done on 06/19/17 Future Value Calculator Investment Amount Yearly Interest Rate: Nurmlpr of Years Future Value: $1,000.00 5% $1,276.28 This calculation was done on 06/19/17