field = $field; $this->error_message = $error_message; } public function getErrorMessage() { return $this->error_message; } public function getField() { if (is_array($this->field)) { return $this->field[0]; } return $this->field; } public function isFieldNotEmpty(array $data) { return isset($data[$this->field]) && $data[$this->field] !== ''; } }