<div class="col-sm-12 col-md-3">
  <select id="country" class="select2" name="country_id">
    <option value="0">Select a country</option>
     <?php $get_country = $db->prepare("SELECT * FROM country ORDER BY id ASC");
     $get_country->execute();
     while ($fetch_country = $get_country->fetch(PDO::FETCH_ASSOC)) { ?>           <option value="<?php echo $fetch_country['id'] ?>"><?php echo $fetch_country['name']; ?></option>
        <?php } ?>
  </select>
</div>
<div class="col-sm-12 col-md-3">
          <select id="city" class="select2" name="city_id">
          </select>
</div>

myDropzone.on('sendingmultiple', function (file, xhr, formData) {

 $("form input, form select").each(function () {
          formData.append($(this).attr("name"), $(this).val());
       }
     formData.append('name', $('#summernote').summernote('code'));
});

<select name="sel1">
    <option value="A">A</option>
    <option value="B">B</option>
</select>

<select name="sel2"></select>


<script>

    imageDropzone.on('sendingmultiple', function(a,b,c) {
        $('select').each(function() {
            alert($(this).val());
        });
    });

    $('[name=sel1]').on('change', function() {
        addOpt();
    });

    function addOpt() {
        $.get('options.html', null, function(){
            $('[name=sel2]').append('<option value="C">C</option>');
        });
    }
</script>