$getdomainslist = mysqli_query ($conn, "SELECT domain FROM domains_kp WHERE userid = '$login'");
<select>
<?php while ($data = mysqli_fetch_array($getdomainslist)) {
echo '<option value ="'.$data['domain'].'" >'.$data['domain']."</option>";} ?>
</select>
$domain = mysqli_fetch_array ($getdomainslist);
print_r($domain);