我需要2个文本字段和1个文件上传。当我只需要文本字段时，一切都正常，但是当我需要文件上传时，即使我选择了一个文件，验证错误仍然会提示需要文件。有人知道我在做什么错吗？提前谢谢了。

//视图

<?php echo form_open_multipart('add'); ?>

<fieldset>
    <input type="text" name="name" /><br>
    <input type="text" name="code" /><br>
    <input type="file" name="userfile" /><br><br>
    <input type="submit"value="Add" />
</fieldset>

<?php echo form_close(); ?>

//控制器

public function add() {

    $this->form_validation->set_rules('name', 'Name', 'required');
    $this->form_validation->set_rules('code', 'Code', 'required');
    //$this->form_validation->set_rules('userfile', 'Document', 'required');
    //when the above line is active the upload does not go through

    if ($this->form_validation->run() == FALSE) {

        $data['page_view'] = $this->page_view;
        $data['page_title'] = $this->page_title;
        $this->load->view('template', $data);
    }
    else
    {
        $this->load->library('upload');

        if (!empty($_FILES['userfile']['name']))
        {
            $config['upload_path'] = './uploads/';
            $config['allowed_types'] = 'gif|jpg|png|jpeg';

            $this->upload->initialize($config);

            if ($this->upload->do_upload('userfile'))
            {
                $img = $this->upload->data();
                $file_name = $img['file_name'];

                $name = $this->input->post('name');
                $code = $this->input->post('code');

                $this->load->model('create', 'create_model');
                $this->create_model->create_entry($name, $code, $file_name);

                $data['page_view'] = $this->page_view;
                $data['page_title'] = $this->page_title;
                $this->load->view('template', $data);
            }
            else
            {
                echo $this->upload->display_errors();

            }
        }
    }
}