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

UPDATE:

I tested again an it seems to be working perfectly if you call a validation array too.  
The only difference with my live example (which throws 'T_VARIABLE' parse error on $this) is that I assign my validation array (cfr. MY_Model - L. Ezell) as the property $validation_rules at the beginning of my extending child class.

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();

    }

...
} 


Now I found this thread: 'Can't concatenate on an array' and the proposed solution was that you have to assign such arrays (containing concanations and even methods starting with $this->) in a method...

So I changed my code (assigned the array in the constructor) to:

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'
             )

          );
   }

...
} 


 And YES: the problem was solved ...

Does anyone has an explanation for this?

Best regards,

Zeff