在过去5天之前付款待定通知显示Php mysqli

Payment notification automatically display before last 5 days.what i tried so far i attached below. no errors there but check whether is this code is correct the way i wrote. example if i select the date 18.12.2018 when save the record. after that before last 5 days in this date 18.12.2018 . notification should display. like this payment pending.

<?php
include("../php/db.php");
if ($_SERVER['REQUEST_METHOD'] == 'GET') {
    $sql = "select id,date,total,pay,due,pay_date,payment_type from sales ";
    $result = $conn->query($sql);
    if ($result->num_rows > 0) {
        while ($row = $result->fetch_assoc()) 
        {
            $id =  $row["id"];
            $paydate =  $row["pay_date"];
            $duedate = date("Y-m-d", mktime(0, 0, 0, date("m"), date("d") + 7));

            if ($duedate >= $paydate) 
            {
                echo  "</br>" .$id.  "  " . "Pending payment" . " "  . $paydate;
            }
        }

    }
}
?>