Displaying Coupons - php

Question

So I have this MySQL table where an item has a field called isCoupon. The default is set to 0 if the seller does not make the item available for coupon use. Each item is ordered by ID and in the shop, there can be more than one coupon where the item is also available for discount. But how do I make it that those coupons display when the item is included? How do I make it that the buyer gets to pick which coupon to use? And how do I calculate the new price if I put "50% off" on the record instead of 0.5?
Table Coupon
couponCode | items | discount
------------------------------
SAMPLE123 | 1 | 50% off
SAMPLE234 | 2,3 | 40% off
SAMPLE345 | 1,5 | 25% off
Table Item
itemID | isCoupon
-----------------
1 | 1
2 | 1
3 | 1
4 | 0
5 | 1
Thanks!

Answer 1

Try the below. As for the buyer picking to choose which coupon, you should let the buyer select the item first and then go to the checkout page by selecting the coupon.
$num_items = 5;
// the below array is used to store the coupons you can use for the item so you can
// proceed with it to the checkout page, there you can make a select dropdown to let
// the buyer select which coupon to use
$coupon_use = array();
for($i = 0; $i < $num_items; $i++) {
// check for current item
$SQL = "SELECT * FROM item WHERE itemID = '$i'";
$result = mysqli_query($connect, $SQL);
$field = mysqli_fetch_assoc($result);
// check if there is a coupon for the current item
if($field['isCoupon'] == 1) {
$SQL2 = "SELECT * FROM coupon";
$result2 = mysqli_query($connect, $SQL2);
// while method to go through every single coupon
while($field2 = mysqli_fetch_assoc($result2)) {
// if you put commas, you can use the explode method
// to store all the items for that coupon and use it to
// check for that current item
$coupons = explode(',', $field2['items']);
if(in_array($i, $coupons)) {
// do your items have a price?
// salePrice is the new price
// thePrice is the old price you need to get with $field (not $field2)
if($field2['discount'] == '50% off') { $salePrice = $thePrice * 0.5; }
else if($field2['discount'] == '40% off') { $salePrice = $thePrice * 0.6; }
else if($field2['discount'] == '25% off') { $salePrice = $thePrice * 0.75; }
// add the coupon code to the array of coupons available for use
array_push($coupon_use, $field2['couponCode']);
// display the prices
echo 'ITEM #'.$i.'<br><s>$'.$thePrice.'</s><br>$'.$salePrice.'<br><br>';
}
}
}
else { echo 'ITEM #'.$i.'$'.$thePrice; }
}
Now you can store the values of the coupon_use array to the checkout page.