<?php
    require_once'conn.php';
    if(ISSET($_POST['use'])){
        $coupon=$_POST['coupon'];

        $query=mysqli_query($conn, "SELECT * FROM `coupon` WHERE `coupon_code`='$coupon'") or die(mysqli_error());
        $row=mysqli_num_rows($query);
        $fetch=mysqli_fetch_array($query);
        if($row > 0){
            if($fetch['status']==''){
                echo "<div class='alert alert-info'>Coupon code activated!</div>";
                mysqli_query($conn, "UPDATE `coupon` SET `status`='used' WHERE `coupon_id`='$fetch[coupon_id]'") or die(mysqli_error());
            }else{
                echo "<div class='alert alert-danger'>Your coupon code has been used!</div>";
            }
        }else{
            echo "<div class='alert alert-danger'>Your coupon code is not available!</div>";
        }
    }
?>