如何用隐藏的表单更新图像？

Question

大家好我是一个新的codeigniter。我已经创建了代码更新图像，隐藏了表单，但我从隐藏的不传递值到形成图像用户文件:(我现在非常需要帮助吗？或者任何人都可以提供有关的源代码将图像更新到codigniter上的数据库。

<form action="<?php echo base_url()."./site_admin/update_menu/".$this->uri->segment(3); ?>" method="post" enctype="multipart/form-data">

        <?php 
        $id = $this->uri->segment(3);
        $sql = $this->db->get_where('menu',array('id_menu' => $id));
        $row = $sql->row(); ?>
        <?php $idcat = $row->cate_id ?>
        <table class="tab" style="width:100%">
        <tr>
        <td>Categories Name:</td>
        <td>
        <select style="padding:6px;background:#C2C2C2;font-weight: bold;" name="cate">
            <?php
            $query = $this->db->get('categories_menu');
            foreach($query->result() as $lazy){
                $select = "";
                if($lazy->id == $idcat){
                    $select = "selected";
                }
                echo "<option $select value='".$lazy->id."'>".$lazy->cate_name_menu."</option>";
            }
            ?>
        </select>


        </td>
    </tr>

    <tr>

    <td>Upload image:</td>

        <td><input type="file" name="userfile"  style="width:190px;height:35px;font-weight: bold;background:#C2C2C2;"  ></td>
        <td><input type="hidden" name="mono" value="<?php echo $row->image; ?>"></td>
        </td>

    </tr>
        <tr>
        <td>Title:</td>
        <td><textarea class="title" name="title" cols="100" rows="4"><?php echo $row->title; ?></textarea></td>
    </tr>
        <tr>
            <td>Description:</td>
        <td><textarea rows="15" name="description" class="dess" ><?php echo $row->description; ?></textarea><td>
            </tr>
            <tr>
        <td>Prices</td>
        <td><textarea class="price" name="price" cols="40" rows="4"><?php echo $row->prices; ?></textarea></td>
        </tr>
        <tr>
        <td></td>
        <td>

        <input style="width:100px; padding:10px;font-weight: bold;background:#1F1F1F;color:white;" type="submit" value="Submit" name="submit">
        </td>
        </tr>
        </table>
    </form>

控制器：     function update_menu（）{

            $id = $this->uri->segment(3);
            $img1 = $this->input->post('userfile');
            $img2 = $this->input->post('mono');
            if($img1 == ""){
                $img1 = $img2;

                $datas = array(
                'cate_id' => $this->input->post('cate'),
                'title' => $this->input->post('title'),
                'description' => $this->input->post('description'),
                'prices' => $this->input->post('price'),
                'image' => $img1
                );
            $this->db->where('id_menu', $id);
            $this->db->update('menu',$datas);
            redirect('./site_admin/edit_menu/'.$id);
            }else{
                $id = $this->uri->segment(3);
                $updata = array(
                'upload_path' => './images/',
                'allowed_types' => 'gif|jpg|png',
                'max_size' => '5000',
                'max_width' => '4000',
                'max_height' => '2800'
                );
            $this->load->library('upload',$updata);
            $this->upload->do_upload('userfile');

            $nampic = $this->upload->data(); 

            $data = array(
                'cate_id' => $this->input->post('cate'),
                'title' => $this->input->post('title'),
                'description' => $this->input->post('description'),
                'prices' => $this->input->post('price'),
                'image' => $nampic['file_name']
                );
            $this->db->where('id_menu', $id);
            $this->db->update('menu',$data);
            redirect('./site_admin/edit_menu/'.$id);
            }
}