cakephp - How to create custom validation for Modelless Forms in cakephp3 -

i want create custom validation fields. form has been extended cakephp form class (modelless forms).

note: bear in mind modelless forms there no table or database.

the problem when create validation give me error.

method isvalidcardnumber not exist

here code:

<?php namespace app\form;  use cake\core\configure; use cake\form\form; use cake\form\schema; use cake\network\exception\socketexception; use cake\validation\validator; use sagepay\sagepaydirectpayment;  /**  * payment form  */ class paymentform extends form {      /**      * define schema      *      * @param  \cake\form\schema $schema schema customize.      * @return \cake\form\schema schema use.      */     protected function _buildschema(schema $schema)     {         return $schema             ->addfield('name', 'string')             ->addfield('card_number', 'string')             ...             ...;     }      /**      * define validator      *       * @param  \cake\validation\validator $validator validator customize.      * @return \cake\validation\validator validator use.      */     protected function _buildvalidator(validator $validator)     {         return $validator                ->notempty('name', 'please enter name on card.')                 ->notempty('card_number', 'string')             ->add('card_number', 'isvalidcardnumber', [                 'rule' =>  ['isvalidcardnumber'],                 'message' => 'card number should 16 long number.'             ])             ...             ...;      }      protected function isvalidcardnumber($data, array $context)     {         debug($data);         die;     } } 

you need set provider.

add object provider.

$validator = new validator();  // use object instance. $validator->provider('custom', $myobject);  // use class name. methods must static. $validator->provider('custom', 'app\model\validation'); 

then use it.

use cake\orm\table; use cake\validation\validator;  class userstable extends table {      public function validationdefault(validator $validator)     {         $validator             ->add('role', 'validrole', [                 'rule' => 'isvalidrole', // <--- method                 'message' => __('you need provide valid role'),                 'provider' => 'table', // <--- provider             ]);         return $validator;     }      public function isvalidrole($value, array $context)     {         return in_array($value, ['admin', 'editor', 'author'], true);     }  } 

the code copy pasted official documentation, alter needed use case.