auth.php

<?php

return [
  'updateModel' => [
    // authItem definition
    'bizRule' => function($params, $data) {
      return my_biz_rule_code();
    }
  ]
];

PhpAuthManager

<?php

class PhpAuthManager extends CPhpAuthManager
{
  // your code
  public function executeBizRule($bizRule, $params, $data)
    {
        $bizRule = $bizRule ? @unserialize($bizRule) : null;
        if (is_callable($bizRule)) {
            return call_user_func_array($bizRule, [$params, $data]);
        }

        return parent::executeBizRule($bizRule, $params, $data);
    }
    // your other code
}