Have been trying to implement the pmt function used in excel into php. I have the formula but the calculations are showing incorrect.
Its 6% interest rate for period of 30 years, final value being 833333.
The right answer should be 10,541.
payments are due at the end of the period so the type is zero and present value is zero.
<pre>
$pv = 0;
$fv = 833333;
$i = 0.06/12;
$n = 360;
$pmt = (($pv - $fv) * $i )/ (1 - pow((1 + $i), (-$n)));
echo $pmt;
</pre>
Using this link as reference for formula
The PMT function calculates loan payments. Since most loan payments are monthly, the function needs to be modified by dividing the interest rate by 12, but multiplying the number of payment periods by 12.
The formula that I use in PHPExcel to reflect MS Excel's formula is:
$PMT = (-$fv - $pv * pow(1 + $rate, $nper)) /
(1 + $rate * $type) /
((pow(1 + $rate, $nper) - 1) / $rate);
where
Which returns the same result as MS Excel when I use
=PMT(6%/12, 360, 0, 833333, 0)
And which returns a result of -10540.755358736 (the same as MS Excel) when I use
=PMT(0.06,30,0,833333,0)
A cleaner solutions is as below.
* @param float $apr Interest rate.
* @param integer $term Loan length in years.
* @param float $loan The loan amount.
function calPMT($apr, $term, $loan)
{
$term = $term * 12;
$apr = $apr / 1200;
$amount = $apr * -$loan * pow((1 + $apr), $term) / (1 - pow((1 + $apr), $term));
return round($amount);
}
function loanEMI()
{
echo $this->calPMT(16, 1, 1020000);
}
This will give you exact PMT as in MS Excel.
Source : https://drastikbydesign.com/blog-entry/excel-pmt-php-cleaner
Heres another one which I came across. Might be of use to someone in future.
$pv = 0;
$fv = 833333;
$i = 0.06;
$n = 30;
$pmt = ((($pv *( pow((1+$i), $n) )) + $fv) * $i ) / (1 - ( pow((1+$i), $n) ));
echo $pmt;
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