Mostrar menú desplegable en HTML con PHP

<div class="form-group">
  <label class="col-md-3 control-label">Admob On/off :-</label>
  <div class="col-md-6">   
   <select class="form-control " type="text" name="ads_status"  >
     <option value="on" <?php if($settings_row['ads_status']== 'on') echo "selected = 'selected'" ?> >On</option>
     <option value="off" <?php if($settings_row['ads_status'] == 'off') echo "selected = 'selected'" ?> >Off</option>
   </select>
  </div>
</div>

Espero que esto te ayude.