code: private function getCallableFunction($method)
      {
          if (is_callable($method)) {
              return $method;
          }
  
          if (is_string($method) && is_callable(array($this, $method))) {
              return array($this, $method);
          }
  
          return FALSE;
      }
docs: Get callable as per given method
  
  @param $method
  @return array|bool|callable