Codeigniter -错误-没有要更新的数据

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Example_model extends CI_Model {

    public function update_data($id, $data) {
        $this->db->where('id', $id);
        $result = $this->db->update('your_table_name', $data);

        if ($result === 0) {
            // 没有数据被更新
            return false;
        } else {
            // 更新成功
            return true;
        }
    }
}

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Example_controller extends CI_Controller {

    public function update() {
        $id = $this->input->post('id');
        $data = array(
            'column1' => $this->input->post('column1'),
            'column2' => $this->input->post('column2')
        );

        $this->load->model('example_model');
        $result = $this->example_model->update_data($id, $data);

        if ($result === false) {
            echo "没有要更新的数据";
        } else {
            echo "更新成功";
        }
    }
}