Something

if ($data == "unavailable" or $data == "") {
   echo "no ratecenters available there";
} else {
       $did = explode("\n", $data);
       foreach ($dids as $i => $value) {
         $info = $value;
         if ($info != "") {
          list($did,$ratecenter,$rate)= split(",", $info, 3);
          echo "Avaible did's in this City: <option value=""></option><option value="'.$did['dids'].'">' . $did['dids'] . '</option>';
         }
     }
}
?></select>
</td></tr>