上传文件并保存到数据库

Question

我是一名新手程序员，而且我的英语不太好。我会问一个关于我的代码的问题。输入图像并将其保存到phpmyadmin中的数据库时，我感到很困惑。即使输入另一个文件，也会显示noimage.jpg。请帮我解决问题。谢谢

if($this->form_validation->run() === FALSE){
        $this->load->view('templates/header');
        $this->load->view('posts/create', $data);
        $this->load->view('templates/footer');
}
else {
        $config['upload_path'] = './assets/images/posts';
        $config['allowed_types'] ='gif|jpg|png';
        $config['max_size'] ='2048';
        $config['max_width'] ='500';
        $config['max_height'] ='500';
        $this->load->library('upload', $config);
        $this->upload->initialize($config);
        if (!$this->upload->do_upload('userfile')) {
           $error = array(
               'error' => $this->upload->display_errors()
            );
           $post_image ='noimage.jpg';

        }
        else {
           //if uploaded        
            $data = array('upload_data' => $this->upload->data());
            $post_image= $_FILES['userfile']['name'];
        }
        $this->post_model->create_post($post_image);           
        redirect('posts');
}