CodeIgniter -如何将表单中的值作为NULL而不是0来发布

$data['field_name'] = $this->input->post('field_name') ?: NULL;

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

class Example extends CI_Controller {

    public function __construct() {
        parent::__construct();
        $this->load->helper('form');
        $this->load->library('form_validation');
    }

    public function index() {
        $this->load->view('example_form');
    }

    public function submit() {
        $this->form_validation->set_rules('field_name', 'Field Name', 'required');

        if ($this->form_validation->run() == FALSE) {
            $this->load->view('example_form');
        } else {
            $data = array(
                'field_name' => $this->input->post('field_name') ?: NULL
            );

            // 假设你有一个模型来处理数据库操作
            $this->load->model('example_model');
            $this->example_model->insert_data($data);

            redirect('example/success');
        }
    }

    public function success() {
        $this->load->view('success');
    }
}