use flags for country list call from SQL in php

i have a form for choose country that list call from sql now how can put flags for all

<div class="col-xs-12 marpad">
  <div class="labelsrch">Going from</div>
  <div class="inputwrp mapmrkr">
    <select class="custmselct padspl" name="nationality" required>
      <option value="" selected="selected">Tell us where are you from</option>
      <?php 
                   foreach($country as $each_countries){
                    ?>
        <option value="<?=$each_countries->iso_code?>">
          <?=$each_countries->country_name?>
        </option>
        <?php
                   }
                   ?>
    </select>
  </div>
</div>