ref.php

<select class="form-control" required id="ploc" name="ploc">
  <option></option>
  <optgroup id="pairport" label="Airports">
    <option value="airport-YES-YES">International Airport</option>
  </optgroup>
  <optgroup id="photel" label="Hotels">
    <?php 
    foreach ($hotels as $hotel) { ?>
      <option value="HOT<?php echo $hotel['id']; ?>-<?php echo $hotel['eligible_shuttle']; ?>-<?php echo $hotel['d2d']; ?>"><?php echo $hotel["hotel_name"]; ?></option>
    <?php } ?>
  </optgroup>
  <optgroup id="psuburb" label="Suburbs">
    <?php 
   foreach ($suburbs as $suburb) { ?>
      <option value="SUB<?php echo $suburb['id']; ?>-<?php echo $suburb['eligible_shuttle']; ?>-<?php echo $suburb['d2d']; ?>"><?php echo $suburb["suburb_name"]; ?></option>
    <?php } ?>
  </optgroup>
</select>