Use anything as a rule and $this->some_model issue

PHP Code:

<?php defined('BASEPATH') OR exit('No direct script access allowed');
    
class User_model extends CI_Model
{    
    protected $table_name = 'test_table';
    
    protected $primary_key = 'id';
    
    protected $protected_attributes = array('submit');
    
    public function __construct()
    {
        //parent::__construct();
        $this->load->database();
    }
    
    public function insert($data)
    {
        $data = $this->protect_attributes($data);

        $data = $this->validate($data);
        
        if($data)
        {
            $this->db->insert($this->table_name, $data);
            $id = $this->db->insert_id();
        
            return $id; // false or id value
        }
        return false;
    }
    
    public function update($id, $data)
    {
        $data = $this->protect_attributes($data);

        $data = $this->validate($data);
        
        $this->db->where($this->primary_key, $id);
        $this->db->set($data);
        
        $result = $this->update($this->table_name);
        
        return $result; // bool
    }
    
    public function validate($data, $type='update')
    {
        foreach($data as $key => $val)
        {
            $_POST[$key] = $val; // To let form validation library use them
        }
        $this->load->library('form_validation');
        
        $this->form_validation->set_rules('cn', 'Common name', 'required');
        $this->form_validation->set_rules('birthdate', 'Birth Date', [
                                                                    'required', 
                                                                    [
                                                                        'whatever_you_name_it', [ $this->usermodel, 'checkdateformat' ]
                                                                    ]
                                                                ]);
        $this->form_validation->set_rules('remark', 'Remark', 'required');
        
        
        if($this->form_validation->run() === true)
        {
            return $data;
            
        }
        else
        {
            return false;
        }
        
    }
    
    public function protect_attributes($row)
    {
        foreach($this->protected_attributes as $attr)
        {
            if(is_object($row))
            {
                unset($row->$attr);
            }
            else
            {
                unset($row[$attr]);
            }
        }
        
        return $row;
    }
    
    public function checkdateformat($date)
    {
        $this->form_validation->set_message('whatever_you_name_it', 'Not a valid date');

        if (preg_match("/^[0-9]{4}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1])$/",$date)) {
            return true;
        } else {
            return false;
        }
    }
}

PHP Code:

// eg.
Class User_model extends MY_Model
{
    protected $table_name = 'test_table';
    protected $primary_key = 'id';
    protected $skip_validation = false;
    protected $protected_attributes = array('submit');

    protected $validation_rules  =  
    array(
        array(
            'field' => 'cn',
            'label' => 'Common name',
            'rules' => 'required'
        ),
        array(
            'field' => 'birthdate',
            'label' => 'Birth Date',
            'rules' => [
                           'required',
                           [
                           'birthdate_callable', [ $this, 'checkdateformat' ]
                           ]
                       ]
        ),
        array(
            'field' => 'remark',
            'label' => 'Remark',
            'rules' => 'required'
        )
    );
    }


    public function __construct()
    {
        //parent::__construct();
        $this->load->database();

    }

...
}

PHP Code:

Class User_model extends MY_Model
{
   protected $table_name = 'test_table';
   protected $primary_key = 'id';
   protected $skip_validation = false;
   protected $protected_attributes = array('submit');

   protected $validation_rules = array();

   
   public function __construct()
   {
       $this->load->database();
       $this->validation_rules = 
           array(
               array(
                  'field' => 'cn',
                   'label' => 'Common name',
                   'rules' => 'required'
               ),
               array(
                   'field' => 'birthdate',
                   'label' => 'Birth Date',
                   'rules' => [
                                  'required',
                                  ['birthdate_callable', 
                                      [ $this, 'checkdateformat' ]
                                  ]
                              ]
              ),
              array(
                   'field' => 'remark',
                   'label' => 'Remark',
                   'rules' => 'required'
             )

          );
   }

...
}