subtracting a percentage from a value in php

Question

Im writing something similar to a coupon code function, and want to be able to handle both set amount codes, as well as percentage amounts.

My code is as follows;

$amount = "25"; // amount of discount
$percent = "yes"; // whether coupon is (yes) a percentage, or (no) a flat amount

if($percent == "yes"){
$newprice = ???????; // subtract $amount % of $price, from $price
}else{
$newprice = $price - $amount; // if not a percentage, subtract from price outright
}

Im searching google as you read this looking for a solution but i thought id post it here as well to help others who may encounter same problem.

Answer 1

How about this?

$newprice = $price * ((100-$amount) / 100);

Answer 2

In addition to the basic mathematics, I would also suggest you consider using round() to force the result to have 2 decimal places.

$newprice = round($price * ((100-$amount) / 100), 2);

In this way, a $price of 24.99 discounted by 25% will produce 18.7425, which is then rounded to 18.74