用于检查一个表中相同数据的codeigniter验证过程

$sort_order=$this->input->post('sort_order','Sort Of Category','trim|required|max_length[128]|xss_clean|is_unique[categories.sort_order]');

Why is the is_unique function not working here?

It should be for set_rules on your form validation on controller

https://www.codeigniter.com/user_guide/libraries/form_validation.html

$this->form_validation->set_rules('sort_order','Sort Of Category','trim|required|max_length[128]|xss_clean|is_unique[categories.sort_order]');

https://www.codeigniter.com/user_guide/libraries/form_validation.html#setting-validation-rules

https://www.codeigniter.com/user_guide/libraries/form_validation.html#rule-reference

<?php 

class Example extends CI_Controller {

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

  public function index() {
     $data['title'] = 'Example';


     $this->form_validation->set_rules('sort_order','Sort Of Category','trim|required|max_length[128]|is_unique[categories.sort_order]');      

     if ($this->form_validation->run() == false) {

            $this->load->view('header', $data);
            $this->load->view('example', $data);
            $this->load->view('footer');

     } else {

         // You can put your update or insert model function here
         redirect('success_controller');

     }
  }

}

$c_name=$this->input->post('c_name');
$sort_order=$this->input->post('sort_order');

$this->load->library('form_validation');

$this->form_validation->set_rules('c_name','Category Name','trim|required|max_length[128]|xss_clean');
$this->form_validation->set_rules('s_order','Sort Order','Sort Of Category','trim|required|xss_clean|is_unique[categories.sort_order]');