问在CodeIgniter中验证表单下拉列表

EN

// first, we can set a validation rule for the input 'country' (our dropdown), in this case it is required, and must be a natural number. You can look up more rules in the CI user guide, and you can write your own functions as well and add them to the 3rd parameter here. I believe some native PHP functions can be used as well.
$this->form_validation->set_rules('country', 'Country', 'required|is_natural');

// the form is not valid! we'll enter this block whenever the form validation rules above are not met, as well as when first going to this controller-action.
if ($this->form_validation->run() == FALSE) {
    // buid your form, there's some CI functions to help with this that I'm using
    $my_form = form_open('user/edit', 'class="superform"')
        . form_fieldset()
        . '<ol>'
        . '<li>'
        . form_label('Country<br/>', 'country')
        // so here is the dropdown, matching the name given to the validation rule we've set, the second parameter takes an array, which I am grabbing from a model, the last parameter is the 'selected; value, which I am grabbing from some variable, if it's not present the first item in the dropdown will obviously be selected
        . form_dropdown('country', $this->Country_model->get_countries_dropdown(), $user->country)
 . form_error('country', ' <em>', '</em>'
        . form_submit('mysubmit', 'Save', 'class="button"')
        . '</li>'
        . '</ol>'
        . form_fieldset_close()
        . form_close()
    );
    // sending the form variable to my view, where i will simply <?=$my_form?> it
    $this->load->view('user_edit', $my_form);
} else {
    // form has validated! do something!
}

$selected = (!empty(set_value('country'))) ? set_value($country) : '';

form_dropdown('country', $this->Country_model->get_countries_dropdown(), $selected)

echo form_dropdown('events', $options, '', $firstItem);

echo form_dropdown('events', $options, set_value('events'), $firstItem);

function select_validate($selectValue)
{
    // 'none' is the first option and the text says something like "-Choose one-"
    if($selectValue == 'none')
    {
        $this->form_validation->set_message('select_validate', 'Please pick one.');
        return false;
    }
    else // user picked something
    {
        return true;
    }
}

$this->form_validation->set_rules('select', 'Select', 'callback_select_validate');

<select name="select">
    <option value="none" <?php echo set_select('select', 'none', true);?> >- Select One -</option>
    <option value="one" <?php echo set_select('select', 'one');?> >Option one</option>
    <option value="two" <?php echo set_select('select', 'two');?> >Option two</option>
</select>