Zend\Diactoros\ServerRequest::validateUploadedFiles PHP Method

    private function validateUploadedFiles(array $uploadedFiles)
    {
        foreach ($uploadedFiles as $file) {
            if (is_array($file)) {
                $this->validateUploadedFiles($file);
                continue;
            }
            if (!$file instanceof UploadedFileInterface) {
                throw new InvalidArgumentException('Invalid leaf in uploaded files structure');
            }
        }
    }