$query = mysqli_query($conn, "SELECT Voucher_Link FROM incentivevoucher");
while ($row = mysqli_fetch_array($query)) {
    $result = $row['Voucher_Link'];
    $uploads = "voucher-inventory/";
    $files1 = scandir($uploads);
    $files = array_diff($files1, $result);
}
foreach ($files as $row2) {
    echo $uploads.$row2.'<br>';
}