使用Codeigniter中的其他输入字段验证可选的图像上载字段

我有问题在Codeigniter如何验证形式时,文件上传是可选的。 我是创建了一个正常的形式,验证两个输入字段和文件上传字段的形式,这是工作良好。

这里是我的查看php文件(新闻)_添加.php)

<?php
    /**
     * Created by PhpStorm.
     * User: Anu
     * Date: 8/31/2018
     * Time: 10:00 PM
     */?>
    <?php include('partials/admin_header.php'); ?>
    <?php include("partials/admin_sidebar.php"); ?>
    <div class="content-wrapper">
        <div class="container-fluid">
            <!-- Breadcrumbs-->
            <ol class="breadcrumb">
                <li class="breadcrumb-item">
                    <a href="<?php echo base_url(); ?>admin/dashboard">Dashboard</a>
                </li>
                <li class="breadcrumb-item active">Test</li>
            </ol>
            <div class="container mb-4">
                <div class="row">
                    <div class="mx-auto col-10">
                        <!-- form user info -->
                        <div class="card">
                            <div class="card-header">
                                <h3>Add News & Event</h3>
                            </div>
                            <div class="card-body">
                                <?php $attributes = array('id'=>'news_add','class'=>'form-horizontal'); ?>
                                <?php echo form_open_multipart('Add/add_data', $attributes); ?>
                                <div class="form-group">
                                    <b>
                                        <?php echo form_label('User Full Name <small class="text-success"> (required) </small>','', $attributes=array("class" => "control-label col-sm-12 col-lg-12 col-md-12 col-xs-12")); ?>
                                    </b>
                                    <div class="col-sm-12 col-lg-12 col-md-12 col-xs-12">
                                        <?php echo form_input('u_name','', $attributes=array("class" => 'form-control col-sm-12 col-lg-12 col-md-12 col-xs-12',
                                            "id"=>"u_name","placeholder"=>"Enter your full name")); ?>
                                        <?php echo form_error('u_name','<div class="text-danger mb-3">', '</div>'); ?>
                                    </div>
                                </div>
                                <div class="col-sm-12 col-lg-12 col-md-12 col-xs-12">
                                    <div class="form-group">
                                        <label for="img">Image <small class="text-success"> (required) </small></label><br>
                                        <div class="form-group">
                                            <input type="file" class="form-control-file" name="userfile" size="20">
                                        </div>
                                        <?php echo form_error('userfile','<div class="text-danger mb-3">', '</div>'); ?>
                                        <?php if(isset($error)) echo "<div class='text-danger mb-3'>$error</div>"; ?>
                                    </div>
                                <div class="form-group">
                                    <div class="col-sm-12 col-lg-12 col-md-12 col-xs-12">
                                        <?php $data = array('
                                            class'=> 'btn btn-success btn-md center mt-2',
                                            'name'=> 'submit',
                                            'value'=>'Register Now',
                                            'type'=>'submit'
                                        ); ?>
                                        <center>
                                            <?php echo form_submit($data); ?>
                                        </center>
                                    </div>
                                </div>
                                <?php echo form_close(); ?>
                            </div><!-- container -->
                        </div> <!--card-body-->
                    </div> <!--mx-auto col-sm-6-->
                </div><!--row-->
            </div><!--container py-3-->
        </div><!-- /.container-fluid-->
    </div><!-- /.content-wrapper-->
    <?php include("partials/admin_footer.php") ?>

在这里我曾经 form_error() 显示每个输入字段和文件字段的相应错误的方法。我还使用了一种额外的方式来显示我在这里使用的其他文件上传错误 <?php if(isset($error)) echo "<div class='text-danger mb-3'>$error</div>"; ?> 这个 $error 变量来自控制器

这是我的控制器类(添加.php)

        <?php
    /**
     * Created by PhpStorm.
     * User: Anu
     * Date: 8/31/2018
     * Time: 10:07 PM
     */

    class Add extends CI_Controller
    {
         public function __construct()
        {
            parent::__construct();
        }
        public function add_data(){

            $this->form_validation->set_rules('u_name', 'News Title', 'required');
            if (empty($_FILES['userfile']['name']))
            {
                $this->form_validation->set_rules('userfile', 'User Image', 'trim|xss_clean|required');
            }
            $config['upload_path']          = './upload/';
            $config['allowed_types']        = 'gif|jpg|png';
            $config['max_size']             = 2048000;
            // if use helper "upload" don't you need load upload helper here like $this->load->library->('upload',$config)
            // and only you need initialize your configuration rules for your file
            // and $config can be other name it is globle array variable to codeigniter framework
            $this->upload->initialize($config);

            if ($this->form_validation->run() == true) {
                if ( ! $this->upload->do_upload('userfile')) {
                // set file upload error here
                $error = array('error' => $this->upload->display_errors());
                $this->load->view('admin/news_add', $error);
            }
            }else{
                $this->load->view('admin/news_add');
            }
        }
    }