[RESOLVED] PHP math help

[webweever]

I have a few variables that I need to do some math on let's call them price, coupon, discount.

Generally speaking the formula would look like this (price - coupon - discount = newprice). How do I prevent PHP from returning a negative value if the sum of the coupon and discount is more than the price of the item?

I'm basically trying to compute the savings on a particular item after using a coupon and a store discount.

<?php
$price = $10; 
$coupon = $5;
$discount = $6;

// This will return a - value but is actually a net gain of $1
$newprice = ($price - $coupon) - $discount;
echo $newprice;

?>

[dagon]

how about:

$total_discount = $coupon + $discount;
if($total_discount > $price){
    //??
}else{
    $newprice = $price - $total_discount;
}

[NogDog]

Or...

$minPrice = 0; // set to lowest allowed price if not 0
$newprice = max($minPrice, $price - $coupon - $discount);

[webweever]

Thanks for the replies. I finally went about it a slightly different way.

<?php
$savings = $totalcpnvalue + $totaldiscount;
$percentsavings = ($savings / $totalshelfprice) * 100;

$percent = sprintf("%1\$u",$percentsavings);
?>

This solves the - number problem however if some or none of the variables have a value I get the old division by zero error.

Any idea how to solve that?

[webweever]

This was my solution.

<?php 
if (!isset($totalshelfprice)) {
	$noItems = "There are no items in this list";
} else {
	$savings = $totalcpnvalue + $totaldiscount;
	$percentsavings = ($savings / $totalshelfprice) * 100;
	$percent = sprintf("%1\$u",$percentsavings);
}
?>