loan calculator

[raouleduke]

I have this script for a loan calculator, however it does not work if the percent financing is 0%. Any ideas.

$term=$_POST[newrate];
		$amount=$_POST[newamt];
		$term1=( $_POST[newrate] / 100 );
		$length=$_POST[newlength];
		$down=$_POST[newdown];
		$addamt=( $amount - $down );

	$ival=( $term1 / 12 );
	$powval=pow( ( 1 + $ival ), -$length);

	$denominator=( 1 - $powval );
	$numerator=( $ival * $addamt);

	$payment=( $numerator / $denominator );

	$payround=round($payment, 2);

	$oldrate = $_POST['newrate'];
	$oldamt = $_POST['newamt'];
	$oldlength = $_POST['newlength'];
	$olddown = $_POST['newdown'];

	$paytitle = "Payment:";
	$payamt ="$".$payround."";

Thanks in advance.

[nemonoman]

I've never seen this payment calculation formula before. Is it legit?

$powval would be 1 if rate =0

In which case

$denominator=( 1 - $powval );

then $denominator =1

in which case:

    $payment=( $numerator / $denominator ); 

is a divide by 0.

I don't see how this formula would provide a loan payment, however.

[raouleduke]

I just did this and it works fine.

if($post == '0'){
		$newrate = 1;
		}else{
		$newrate = $_POST[newrate];
		}

Thanks for your input.

[nemonoman]

Yes, you won't get a divide by 0 error if you try that. But I thought you were trying to output the loan payment amount for a given rate. The answer your script provides certainly wouldn't amortize the loan over time.

Compare to this amortization calculator:

http://dave.imarc.net/php/mortgage/index.php