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<?php
//define present value
$presentValue = 100000;

//define interest rate per compounding period
$intRate = 8;

//define number of compounding periods
$numPeriods = 6;

//calculate future value assuming compound interest
//result: "100000 @ 8 % over 6 periods becomes 158687.43"
$futureValue = round($presentValue * pow(1 + ($intRate/100),↵
$numPeriods), 2);
echo "$presentValue @ $intRate % over $numPeriods periods becomes ↵
$futureValue";
?>

The formula to calculate the future value (F) of a particular amount (P), given a fixed interest rate ( r ) and a fixed number of years ( n ), is F = P(1 + r/100)n. Nevertheless, you will be surprised how many novice programmers forget all about PHP's operator precedence rule. Then, for the result, they generate incorrect results.