Comments on: Time Value of Money – Excel PMT in JavaScript and PHP

By: David C

David C — Sat, 15 May 2010 15:10:21 +0000

just determined how to get payment at beginning of period …

intPayment = -(intInterestRate * intPrincipal * Math.pow((1 + intInterestRate), intMonthCount – intFlagPmtBegPeriod) / (1 – Math.pow((1 + intInterestRate), intMonthCount)));

I changed the variable names, and added the negative sign, but otherwise same as original, except for the flag.

// intInterestRate = Interest rate per month (.05 / 12, .06 / 12, .07 / 12, …).
// intPrincipal = Amount to borrow.
// intYearCount = Number of years to pay back loan.
// intFlagPmtBegPeriod = Whether payment occurs at beginning of period (month). 1 = Yes. 0 = No.

By: Rupert Millard

Rupert Millard — Thu, 04 Mar 2010 14:28:52 +0000

This is really helpful – thank you.

By: Stuart

Stuart — Wed, 27 Jan 2010 08:04:48 +0000

In php –
return $i * ($p * pow((1 + $i), $n) + $fv) / (1 – pow((1 + $i), $n));

will allow for “future value” functionality – Don’t forget to add the $fv variable into your function call

These equations works for payment in arrears only.. Still scratching my head as to how to formulate the PMT as a payment in advance.

Thanks for the article. It’s been the backbone of calculator I’ve been trying to complete.

By: ?????????

????????? — Sun, 27 Sep 2009 08:27:16 +0000

Thnaks alot!

By: BeN

BeN — Tue, 22 Sep 2009 15:39:29 +0000

Hi, i spend a lot of time trying to make this (in php) and many hours on google looking for this. Thankssssssss

By: brokencode

brokencode — Sat, 15 Aug 2009 14:09:02 +0000

thanks for sharing. how about PV and Fv function to calculate annuity.