retrievePlaceholders example

    protected function fillPlaceholders(array $rules, array $data): array
    {
        foreach ($rules as &$rule) {
            $ruleSet = $rule['rules'];

            foreach ($ruleSet as &$row) {
                if (is_string($row)) {
                    $placeholderFields = $this->retrievePlaceholders($row, $data);

                    foreach ($placeholderFields as $field) {
                        $validator ??= Services::validation(null, false);
                        assert($validator instanceof Validation);

                        $placeholderRules = $rules[$field]['rules'] ?? null;

                        // Check if the validation rule for the placeholder exists                         if ($placeholderRules === null) {
                            throw new LogicException(
                                'No validation rules for the placeholder: ' . $field
                            );