[RESOLVED] Division by Zero

Warmaster

I have researched this topic and I understand I can use a @ sign in front of my function to suppress the warning, however, I would like to understand this more so I know how to program properly. So, once again I bring this same code up that is bewildering me:

 <?
function calcMonthlyPayment($amount, $int, $term)
{
     $monthly_int = $int/1200;  //Monthly Interest J
     $total_amt = $amount;  //Loan Amount P
     $months = $term * (-12);  //Length of Note in months  N
     $payment = $total_amt * $monthly_int / (1 - pow(1+$monthly_int, $months ));  //Determining Monthly Payment
     $payment = number_format($payment, 2);  //Returning Monthly Payment in a dollar amount

			return $payment;   //Show me the money
}
$check = calcMonthlyPayment(200000, 5.78, 30);
echo "<p>$check</p>"; ?>

This returns $1,170.96 and NO division by zero warning.

I have included functions.php which is where the above code is stored and I have cut and pasted the $check and echo lines into the following page:

<?php 
include ('functions.php');

//determine monthly payment
$monthly_payment = calcMonthlyPayment ($amount, $rate, $term);

// Determining the vacancy adjustment  

$vacancy_loss = calcVacancyLoss ($rent, $vacancy);

$check = calcMonthlyPayment(200000, 5.78, 30);
echo "<p>$check</p>";

?>

It gives me the right division and the math is right on but, I still get a Warning: Division by zero in line 8 which is this line:

 $payment = $total_amt * $monthly_int / (1 - pow(1+$monthly_int, $months ));  //Determining Monthly Payment

When I print out the denominator by itself, it comes up with 0.8....... which is not 0...therefore how can I get a division by zero error? Thanks for the help in understanding this.

warmaster

bradgrafelman

What version of PHP are you running, and what is your error_reporting level? Are you positive this error is reproducible using the isolated code snippet you provided?

I copied the first code snippet and it ran fine without warnings on both PHP 4.4.7 and 5.2.2 (just happened to be the two versions I have on this computer). My error_reporting is set to E_ALL on PHP4 and E_ALL | E_STRICT on PHP5.

HalfaBee

You shouldn't, you could try casting it to (float) and see if that helps.

$payment = $total_amt * $monthly_int / (float) (1 - pow(1+$monthly_int, $months ));

Warmaster

I tried (float) and got the same division by zero results. I am not positive that the warning would be replicated with just the above provided code..silly me. Here are the files in their entirety:

functions.php:

<?php 

function calcMonthlyPayment($amount, $int, $term)
{
     $monthly_int = $int/1200;  //Monthly Interest J
     $total_amt = $amount;  //Loan Amount P
     $months = $term * (-12);  //Length of Note in months  N
		 //$payment = $total_amt * $monthly_int / (1 - pow(1+$monthly_int, $months ));  //Determining Monthly Payment
		 $payment = $total_amt * $monthly_int / (float) (1 - pow(1+$monthly_int, $months ));
		 $payment = number_format($payment, 2);  //Returning Monthly Payment in a dollar amount

			return $payment;   //Show me the money
}


function calcVacancyLoss($monthly_rent, $vacancy_percentage) {
     $monthly_rent = $monthly_rent;
		 $vacadj = $monthly_rent * ($vacancy_percentage / 100);
		 $vacadj = number_format($vacadj, 2);

	 return $vacadj;
}

?>

handle_form.php:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>
<head>
<title>Untitled</title>
</head>
<body>
<?php 
include ('functions.php');
//assigning variables for the Property Details
$bedrooms = $_POST['bedrooms'];
$bathrooms = $_POST['bathrooms'];
$garage = $_POST['garage'];
$sq_footage = $_POST['sq_footage'];
$acreage = $_POST['acreage'];
$patio = $_POST['patio'];
$pool = $_POST['pool'];
$spa = $_POST['spa'];
$comment = $_POST['comment'];

//Assigning variables for the Monthly Expenses
$utilities = $_POST['utilities'];
$taxes = $_POST['taxes'];
$insurance = $_POST['insurance'];
$other = $_POST['other'];
$repairs = $_POST['repairs'];

//Assigning variables for the Income Information
$rent = $_POST['rent'];
$vacancy = $_POST['vacancy'];

//assigning variables for the purchasing of the property
$amount = $_POST['amount'];
$term = $_POST['term'];
$rate = $_POST['rate'];

//determine monthly payment
$monthly_payment = calcMonthlyPayment ($amount, $rate, $term);

// Determining the vacancy adjustment  

$vacancy_loss = calcVacancyLoss ($rent, $vacancy);

//Determine the Net Operating Income
$noi = ($rent * $vacadj) - $utilities - $taxes - $insurance - $other - $repairs;

$check = calcMonthlyPayment(200000, 5.78, 30);
echo "<p>$check</p>";
?>

</body>
</html>

I am confused by this lol, but thanks for your help bradgrafelman and HalfaBee (again 🙂

-edit almost forgot, using PHP 5.2.6 and error reporting set to E_ALL

warmaster

bradgrafelman

I copied your functions.php file exactly, and ran this test code:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>
<head>
<title>Untitled</title>
</head>
<body>
<?php
include ('functions.php');

$check = calcMonthlyPayment(200000, 5.78, 30);
echo "<p>$check</p>";
?>

</body>
</html>

Again, no errors/warnings appeared. If you're still getting the warning, try using [man]var_dump/man on pieces of the denominator. For example, does placing this:

var_dump((1 - pow(1+$monthly_int, $months )));

just above the return statement produce:

float(0.82268674554978)

Warmaster

yes..it returns this:

int(0)
Warning: Division by zero in C:\wamp\www\PHP Learning\Property Evaluation\functions.php on line 8
float(0.82268674554978)
Warning: Division by zero in C:\wamp\www\PHP Learning\Property Evaluation\functions.php on line 8

0.00

-edit, the weird thing about this is, I do not get the warning when I place the $check inside the functions.php just as you have experienced. It is only including it in that second file that I start to get the warnings...if that helps at all.

warmaster

HalfaBee

Try echoing all the variables being used, you will probably find they are 0

Warmaster

Ok, I figured it out and I am confused by how it is affecting me by the warning:

if I comment out this line in handle_form.php:

$monthly_payment = calcMonthlyPayment ($amount, $rate, $term);

I get no error and it works accordingly. I am confused since I did not make any changes to the function itself and I called the function straight from the functions.php. Obviously all I did above was call the function and assign it to a variable for a later piece of code I will be adding, so how does $monthly_payment affect $check? I did echo the variables and all but one had a value. Thanks for the help,

warmaster

HalfaBee

You are obviously not passing values to the function.
Check your $_POST array to see what is being sent from the form.

Warmaster

Well, lol maybe that is my problem. I knew I wasn't passing values to the function since I didn't submit the form. I just opened the handle_form.php as a stand alone. I just thought since it wouldn't have passed values to the first function that it wouldn't affect the second function. I guess I was wrong. Thanks for the help HalfaBee and bradgrafelman