<?php 
    // DP style
    $rules_delete_exception = array();
    $rules_delete_exception[] = 'booker_name {
        required: true
    }';

    $this->formhelper->setupJsFormValidation('confirm_form', '{'.implode(', ', $rules_delete_exception).'}', $messages='{}', $submit_handler='default');
?>

<!-- action button -->
<button type="button" class="btn bg-danger" data-toggle="modal" data-target="#confirm_modal">Confirm</button>

<!-- Modal to confirm action initially hidden -->
<div id="confirm_modal" class="modal fade" tabindex="-1">
    <?php echo form_open('controller/method', array('id' => 'confirm_form')); ?>
        <input type="text" name="booker_name">
            <button type="button" data-dismiss="modal">Close</button>
            <button type="submit">Yes, delete exception</button>
        </div>
    </form>
</div>

<script>
    // Jquery style
    const fv = FormValidation.formValidation(confirm_form, {
        rules: {
            'booker_name', {required: true }
        },

    });
</script>