> For clean Markdown content of this page, append .md to this URL. For the complete documentation index, see https://buildwithfern.com/learn/llms.txt. ## 2.22.0 **`(feat):`** Object types with XML encoding metadata (e.g. TwiML) now extend `XmlSerializableType` and generate `toXml()`/`toXmlElement()`, `fromXml()`/`fromXmlElement()`, and fluent child builder methods (`$response->say('Hello', ['voice' => 'man'])`). Attributes, text, namespaces, prefixes, wrapped lists, separator-delimited lists and enums round-trip; unknown attributes and children are preserved and re-emitted, and parsing rejects DTDs, malformed input and wrong root elements. XML types add `ext-dom`/`ext-libxml` to `composer.json` and a `Core\Xml` runtime.