无法在 codeigniter 中保存 1 个表单中的 2 个文件

I have a form that requires a user to upload 2 files, file-upload & imgupload. I am trying to save the entire form through ajax.

表单和ajax代码

<form enctype="multipart/form-data" id="data">
  <input type="file" id="file-upload" class="file-upload" name="file-upload" >
  <input type="file" id="imgupload" class="imgupload" name="imgupload"  >

  <button type="submit" id="save" class="save-icon-btn">
    <img src="<?php echo base_url(); ?>assets/img/Save.png">
  </button>
</form>

$("#save").click(function()
  {
    var form_data = new FormData($('#data')[0]);
    jQuery.ajax(
      {
        type: "POST",
        url: "<?php echo base_url(); ?>" + "comp/wfc",
        data: form_data,
        processData: false,
        contentType: false,
        success: function(res) 
          {
            console.log(res);
            alert(res);
          }
      });
  });

控制器代码

$config['upload_path'] = './assets/file/.';
$config['allowed_types'] = 'gif|jpg|png|doc|txt';
$config['max_size'] = 1024 * 8;
$config['encrypt_name'] = TRUE;

$this->load->library('upload', $config);
$this->upload->initialize($config);

if (!$this->upload->do_upload('file-upload')) 
  {
    $error = array('error' => $this->upload->display_errors());
     print_r($error);
  }
else
  {
    $data = $this->upload->data();
    echo $res = $data['file_name'];
  }


$config2['upload_path'] = './assets/img/.';
$config2['allowed_types'] = 'gif|jpg|png|doc|docx|txt';
$config2['max_size'] = 1024 * 8;
$config2['encrypt_name'] = TRUE;

$this->load->library('upload', $config2);

if (!$this->upload->do_upload('imgupload')) 
  {
    $error1 = array('error' => $this->upload->display_errors());
    print_r($error1);
  }
else
  {
    $data1 = $this->upload->data();
    echo $res1 = $data1['file_name'];
  }

问题是在控制器代码中只有 1 个文件被上传.如果我将文件上传作为第一个上传代码，那么只有这个会被上传，而 imgupload 不会被上传.

        $this->load->library('upload');

        echo '<pre>';
        print_r($_FILES);

        $config['upload_path'] = './assets/file/.';
        $config['allowed_types'] = 'gif|jpg|png|doc|txt';
        $config['max_size'] = 1024 * 8;
        $config['encrypt_name'] = TRUE;
        $this->upload->initialize($config);

        if (!$this->upload->do_upload('file-upload')) {
            $error = array('error' => $this->upload->display_errors());
            print_r($error);
        } else {
            $data = $this->upload->data();
            echo $res = $data['file_name'];
        }

        $config2['upload_path'] = './assets/img/.';
        $config2['allowed_types'] = 'gif|jpg|png|doc|docx|txt';
        $config2['max_size'] = 1024 * 8;
        $config2['encrypt_name'] = TRUE;

        $this->upload->initialize($config2, true);

        if (!$this->upload->do_upload('imgupload')) {
            $error1 = array('error' => $this->upload->display_errors());
            print_r($error1);
        } else {
            $data1 = $this->upload->data();
            echo $res1 = $data1['file_name'];
        }