验证不适用于选择drpo-down菜单

Question

我有这个选择菜单：

<select name="category_id" class="form-control ">
    <option selected>Select Category</option>
    <?php foreach($categories as $category): ?>
        <option value="<?php echo $category->id; ?>"><?php echo $category->name; ?></option>
    <?php endforeach ; ?>
</select>

我的控制器中有下一个规则：

$this->form_validation->set_rules('category_id','Category','required');

其他输入字段的其他一些规则，它们正在运行，但它忽略了这个下拉select菜单。

  

完整表单视图：

<!-- Display Validation errors -->
<?php echo validation_errors('<p class="alert alert-dismissable alert-danger">'); ?>
<form method="post" action="<?php echo base_url() ?>admin/articles/add">
    <div class="row">   
      <div class="col-md-6">
        <h1 class="sub-header">Add Article</h1>
      </div>
    </div>
            <ol class="breadcrumb">
                <li>
                    <a href="<?php echo base_url();?>admin/dashboard">
                        Dashboard
                    </a>
                </li>
                <li>
                    <a href="<?php echo base_url();?>admin/articles">
                        Articles
                    </a>
                </li>
                <li>
                    Add Article
                </li>
            </ol>

            <div class="form-group">
                <label>Article Title</label>
                <input type="text" class="form-control" name="title" value="<?php echo set_value('title'); ?>" placeholder="Enter Title" />
            </div>

            <div class="form-group">
                <label>Category</label>
                <select name="category_id" class="form-control ">
                    <option selected>Select Category</option>
                    <?php foreach($categories as $category): ?>
                        <option value="<?php echo $category->id; ?>"><?php echo $category->name; ?></option>
                    <?php endforeach ; ?>
                </select>
            </div>

            <div class="form-group">
                <label>Article Text</label>
                <textarea class="form-control" name="body" rows="10" value="<?php echo set_value('body'); ?>" > </textarea>
            </div>


            <div class="form-group">
                <label>Access</label>
                <select name="access" class="form-control ">
                    <option selected>Select Group</option>
                    <option value="0">Everyone</option>
                    <?php foreach($groups as $group) : ?>
                        <option value="<?php echo $group->id; ?>"><?php echo $group->name; ?></option>
                    <?php endforeach; ?>
                </select>
            </div>

            <div class="form-group">
                <label>Author</label>
                <select name="user_id" class="form-control ">
                    <option selected>Select Author</option>
                    <?php foreach($users as $user): ?>
                        <option value="<?php echo $user->id; ?>"><?php echo $user->username; ?></option>
                    <?php endforeach; ?>
                </select>
            </div>

            <div class="form-group">
                <label>Published</label>
                <br />
                <label class="radio-inline">
                  <input type="radio" name="is_published" value="1"> Yes
                </label>
                <label class="radio-inline">
                  <input type="radio" name="is_published" value="0"> No
                </label>
            </div>

            <div class="form-group">
                <label>Add to Navbar</label>
                <br />
                <label class="radio-inline">
                  <input type="radio" name="in_navbar" value="1"> Yes
                </label>
                <label class="radio-inline">
                  <input type="radio" name="in_navbar" value="0"> No
                </label>
            </div>

            <div class="form-group">
                <label>Order</label>
                <input class="form-control" style="width:60px;" type="number" name="order" value="0" min="0" />
            </div>

        <div class="btn-group pull-left">
            <input type="submit" name="submit" id="page_submit" class="btn btn-primary" value="Add" />
            <a href="<?php echo base_url()?>admin/dashboard" class="btn btn-default">Back</a>
        </div>
</form>

  

完全控制器方法：

    public function add(){
    //Validation Rules
    $this->form_validation->set_rules('title','Title','trim|required|min_length[4]|xss_clean');
    $this->form_validation->set_rules('category_id','Category','required');
    $this->form_validation->set_rules('body','Body','trim|required|xss_clean');
    $this->form_validation->set_rules('is_published','Publish','required');


    $data['categories'] = $this->Categories_model->get_categories();
    $data['users'] = $this->User_model->get_users();
    $data['groups'] = $this->Groups_model->get_groups();

    //Checking if form was validated
    if($this->form_validation->run() == FALSE){
        //Views
        $data['main_content'] = 'admin/articles/add';
        $this->load->view('admin/layouts/main',$data);
    } else {
        //Create Articles Data Array
        $data = array(
            'title'             => $this->input->post('title'),
            'body'              => $this->input->post('body'),
            'category_id'       => $this->input->post('category_id'),
            'user_id'           => $this->input->post('user_id'),
            'access'            => $this->input->post('access'),
            'is_published'      => $this->input->post('is_published'),
            'in_navbar'         => $this->input->post('in_navbar'),
            'order'             => $this->input->post('order'),
        );

        //Insert into Articles Table
        $this->Article_model->insert($data);

        //Create Notification
        $this->session->set_flashdata('article_saved','Your article was saved!');

        //Redirect
        redirect('admin/articles');
    }

}