If you are using validation, you need to provide a translation. This library uses the PHPFUI\Translation class, or provide a callback with the following parameter signature:
function translate(string $text, array $values = []) : string;
Due to static initialization issues on PHP, you will need to initialize the translation via the setTranslationCallback method.
You will need to copy the provided translations (in ./translations directory) into your project or specify the path to the vendor directory.
\PHPFUI\ORM::setTranslationCallback(\PHPFUI\Translation\Translator::trans(...));
\PHPFUI\Translation\Translator::setTranslationDirectory(__DIR__ . '/../vendor/phpfui/orm/translations');
\PHPFUI\Translation\Translator::setLocale(\Locale::getDefault());