How to use CodeIgniter set_select() together with Chosen Plugin?

Question

I am using CI together with Chosen plugin for tags in my website. I need to populate tags from database and let user add/remove tags and update database on validation->run().

View file:

    <select id="tag-edit-select-bar" multiple="true" class="form-control" name="tag_edit_select_bar">
      <?php foreach ($tags_all as $tag): ?>
        <option value="<?php echo $tag['id']; ?>" <?php echo set_select('tag_edit_select_bar',$tag['id'], ( in_array($tag['id'], $listOfTags ) ? TRUE : FALSE )); ?>><?php echo $tag['name']; ?></option>
       <?php endforeach; ?>
    </select>
    <script>
    $(document).ready(function(){
        $('#tag-edit-select-bar').chosen();
    });
    </script>

where the third parameter of set_select() deals with selecting tags that user allready has in database.

Problem is that on submitting I get back only one value. If I make changes to selection new values are sent to server

...
X-Requested-With:XMLHttpRequest
Form Data
view source
view URL encoded
phone:988987897
tag_edit_select_barr:1
tag_edit_select_barr:3
tag_edit_select_barr:4

but checking in server side with var_dump($this->input->post('tag_edit_select_bar')); gives me only the highest value

but checking in server side with var_dump($this->form_validation->set_value('tag_edit_select_bar')); gives me empty.

I think it has to do with how Chosen plugin allow multiple selects. It seems that CI does not allow that.