NPER function for php

<?php
function Nper($interest, $payment, $loan)
{
    $interest = $interest / 1200;
    $nperC = Log10($payment/ ($payment- $loan * $interest)) / Log10(1 + $interest);
    return $nperC;
}

//$months = Nper($_POST['interest'], $_POST['payment'], $_POST['loan']);
$months = Nper(8.3/1200, 27503, 3099487);

echo round($months,2);
?>