discount vouchers with max cashback on php - php

Question

I want to make a discounted php formula with a voucher but must have a maximum cashback.
example: 20% discount with a maximum of 40000 cashback.
case: if inputted with the price of 100000 with a 20% voucher, the cashback earned is 20000, but if the inputted price is 500000 with a voucher of 20% also then the cashback is only 40000.
help me to solve it, I have searched Google but found no solution.
I have this script :
my script :
<?php
require_once 'conn.php';
$coupon_code = $_POST['coupon'];
$price = $_POST['price'];
$totalorder = $_POST ['totalorder'];
$query = mysqli_query($conn, "SELECT * FROM `coupon` WHERE `coupon_code` = '$coupon_code' && `status` = 'Valid'") or die(mysqli_error());
$count = mysqli_num_rows($query);
$fetch = mysqli_fetch_array($query);
$array = array();
if($count > 0){
$discount = $fetch['discount'] / 100;
$total = $discount * $price;
$array['discount'] = $fetch['discount'];
$array['price'] = ($price - $total) * $totalorder;
echo json_encode($array);
}else{
echo "error";
}
?>

Answer 1

I hope this is what you expected :
<?php
function voucher_calc($price, $max, $voucher){
$discount = $price * $voucher;
if($discount >= $max){
return $max;
}else{
return $discount;
}
}
$price = 500000;
$voucher = 0.2;
$max = 40000;
echo voucher_calc($price, $max, $voucher);