HTML选择所需的验证

I want to validate select option but it's not working for me this is my source code

<?php echo form_open_multipart('dashboard/add_item') ?>

 <select name="provinsi_id" id='propinsi_id' required>
     <option value="0">-Select Category-</option>
     <option value="1">Graphics</option>
     <option value="2">Fonts</option>
     <option value="3">Prints Template</option>
  </select>

   <button type="submit" class="button big dark">Next<span class="primary"> Step</span></button>

<?php echo form_close(); ?>

required on a <select> will reject if the selected option has no value.

Try setting the value on the first option to "" instead of "0".

<option value="">-Select Category-</option>