Codeigniter使用不同的区域名称进行多次上传，并在上传之前重命名该文件

I have a problem with multiple files upload with different area name and want to change for every area filename before it's upload.

This is HTML form.

<input type="file" placeholder="" name="profilPic"/>
<input type="file" placeholder="" name="topPic"/>

This is controller

    $config['upload_path']          = './uploads/';
    $config['allowed_types']        = 'gif|jpg|png';
    $config['max_size']             = 100;
    $config['max_width']            = 1024;
    $config['max_height']           = 768;
    //$config['file_name']          = $this->session->sersession["id"];
    $this->load->library('upload', $config);
    $profilPic = $this->upload->do_upload('profilPic');
    if (!$profilPic){
        $error = array('error' => $this->upload->display_errors());
        $this->session->set_flashdata("error", "profil pic was not uploaded= ");
    }else{
        $data = array('upload_data' => $this->upload->data());
        $this->session->set_flashdata("success", "profil picture was uploaded.");
    }
    $topPic = $this->upload->do_upload('topPic');
    if (!$topPic){
            $error = array('error' => $this->upload->display_errors());
            $this->session->set_flashdata("error", "top pic was not uploaded" );

    }else{
        $data = array('upload_data' => $this->upload->data());
        $this->session->set_flashdata("success", "this picture was uploaded.");
    }

Note: The pictures are upload to directory. But i want to rename every file file name before uploaded like "userID_profil.jpg" and "userID_top.jpg"