feat(php): generate toXml()/fromXml()/builders for xml-encoded object types (TwiML)

[devin-ai-integration]

Description

Linear ticket: Refs (none)

PHP counterpart of #17734 (Python), #17755 (Java), #17785 (TS), #17787 (C#) and #17792 (Go). Object types carrying IR xml encoding metadata (from #17732, IR 67.25.0) now generate XML serialization, parsing and fluent child builders — the TwiML helper-library surface.

$response = new Response();
$response->say('Hello', ['voice' => 'Polly.Joanna'])->break(['strength' => 'strong']);
$dial = $response->dial('+1555', ['record' => ['record-from-answer']]);
$dial->addNumber('+1444', ['sendDigits' => 'ww12']);   // `number` is Dial's text field → add-prefix
echo $response;   // <?xml version="1.0" encoding="UTF-8"?><Response><Say voice="Polly.Joanna">Hello<break strength="strong"/></Say>...

$parsed = Response::fromXml($xml);   // typed children, unknown attrs/children preserved

Changes Made

• generators/php/base/src/asIs/Xml/*: new Core\Xml runtime (DOM/libxml only) — XmlElement generic node, XmlNode interface, XmlSerializableType base (extends JsonSerializableType, holds unknown XML attributes/children + addChild()), XmlUtils (secure parser rejecting DOCTYPE/external entities, root-name/namespace validation, scalar/enum/list parsing, wrapped-list merge of unknown content). Emitted only when the IR contains xml-encoded types; composer.json then also requires ext-dom/ext-libxml.
• generators/php/model/src/object/XmlObjectGenerator.ts: for xml-encoded objects generates toXmlElement(), toXml(bool $xmlDeclaration = false), fromXml(string), fromXmlElement(XmlElement), __toString() (declaration included for root types only), and one builder per child type (say(Say|string|null $message = null, array $attributes = []): Say), with the shared add-prefix collision rule. Enum-typed values go through XmlUtils::parseEnum/enumValues so PHPStan keeps the enum literal unions in the generated array shapes.
• ObjectGenerator.ts: xml objects extend XmlSerializableType instead of JsonSerializableType.
• IR pin 67.21.0 → 67.25.0 for php-base/model/sdk.
• New php-xml-twiml seed fixture (roots, nested children, attributes, namespaces/prefixes, wrapped lists, separator lists, enum lists, empty elements, 64-attr Wide, number/Number collision) registered in seed/php-sdk/seed.yml; changelog under generators/php/sdk/changes/unreleased/.
• Updated README.md generator (not applicable)

Testing

• Unit tests added/updated — XmlElementTest ships as a core test in generated SDKs.
• Manual testing completed
  • pnpm turbo run compile --filter @fern-api/php-sdk: 18/18 tasks; biome clean.
  • pnpm seed test --generator php-sdk --fixture php-xml-twiml --skip-scripts --local: 1/1.
  • Generated SDK: composer install + PHPUnit OK (98 tests, 369 assertions) including a 13-case TwiML round-trip suite (builders, fromXml typed children, enum lists, wrapped lists, unknown attrs/children incl. prefixed x:extra, unknown wrapper content, Wide, empty elements, malformed/empty/wrong-root/wrong-namespace/DTD/invalid-enum/invalid-int errors); PHPStan exit 0 on src + tests.
  • exhaustive fixture regenerated: 0 xml-related diff (only pre-existing drift from main, reverted).

Known/shared limitation (same as the other languages): unknown children are re-emitted after typed children, so arbitrary mixed ordering isn't preserved.

Link to Devin session: https://app.devin.ai/sessions/311fe13ae5434245ada665a9b824809b
Open in Devin Desktop: https://app.devin.ai/desktop/session/311fe13ae5434245ada665a9b824809b?variant=devin

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Docs Generation Benchmark Results

Comparing PR branch against median of 5 nightly run(s) on main (latest: 2026-09-18T04:06:24Z).

Fixture	main	PR	Delta
docs	266.3s (n=5)	263.1s (35 versions)	-3.2s (-1.2%)

Docs generation runs fern generate --docs --preview end-to-end against the benchmark fixture with 35 API versions (each version: markdown processing + OpenAPI-to-IR + FDR upload).
Delta is computed against the nightly baseline on main.
Baseline from nightly run(s) on main (latest: 2026-09-18T04:06:24Z). Trigger benchmark-baseline to refresh.
Last updated: 2026-09-18 22:27 UTC

[github-actions]

SDK Generation Benchmark Results

Comparing PR branch against median of 5 nightly run(s) on main (latest: 2026-09-18T04:06:24Z).

Full benchmark table (click to expand)

Generator	Spec	main (generator)	main (E2E)	PR (generator)	Delta
csharp-sdk	square	82s (n=5)	113s (n=5)	60s	-22s (-26.8%)
go-sdk	square	124s (n=5)	295s (n=5)	147s	+23s (+18.5%)
java-sdk	square	187s (n=5)	268s (n=5)	154s	-33s (-17.6%)
php-sdk	square	65s (n=5)	N/A	65s	+0s (+0.0%)
python-sdk	square	142s (n=5)	257s (n=5)	99s	-43s (-30.3%)
ruby-sdk-v2	square	93s (n=5)	112s (n=5)	58s	-35s (-37.6%)
rust-sdk	square	181s (n=5)	204s (n=5)	150s	-31s (-17.1%)
swift-sdk	square	58s (n=5)	435s (n=5)	54s	-4s (-6.9%)
ts-sdk	square	136s (n=5)	139s (n=5)	108s	-28s (-20.6%)

main (generator): generator-only time via --skip-scripts (includes Docker image build, container startup, IR parsing, and code generation — this is the same Docker-based flow customers use via fern generate). main (E2E): full customer-observable time including build/test scripts (nightly baseline, informational). Delta is computed against generator-only baseline.
⚠️ = generation exited with a non-zero exit code (timing may not reflect a successful run).
Baseline from nightly runs on main (latest: 2026-09-18T04:06:24Z). Trigger benchmark-baseline to refresh.
Last updated: 2026-09-18 22:28 UTC