Fix nullable PHP model hydration for empty strings

[ChiragAgg5k]

Summary

• normalize empty-string values to null during PHP model hydration when the generated property type is nullable
• keep the change scoped to nullable non-builtin from()-hydrated values so optional enum/model fields no longer throw on wire-level "" sentinels

Context

The PHP generator now emits nullable model properties for some response fields, but the shared ArraySerializable hydrator still passed "" into Type::from(...). That causes hydration failures for nullable enum-like fields where the API uses an empty string as an unset sentinel.

Testing

• docker run --rm -v $(pwd):/app -w /app php:8.3-cli php example.php php
• composer lint-twig
• vendor/bin/phpunit tests/PHP83Test.php

[greptile-apps]

Greptile Summary

This PR adds a narrow three-line guard to ArraySerializable::hydrateValue that normalizes an empty-string wire value to null when the target type is nullable and exposes a from() method. The fix is correctly placed after the !method_exists guard (the ordering concern raised in the previous review thread has been addressed in the head commit), so it only fires for nullable, from()-backed non-builtin types.

Confidence Score: 5/5

Safe to merge — the fix is minimal, correctly scoped, and the prior guard-ordering concern is resolved.

Single-file change with a 3-line guard that is logically correct; previous reviewer concern about ordering was addressed in the refining commit; no other issues found.

No files require special attention.

Important Files Changed

Filename	Overview
templates/php/src/Models/ArraySerializable.php.twig	Adds a 3-line guard in hydrateValue that returns null for empty-string wire values when the parameter type is nullable and has a from() method; correctly placed after the method_exists guard.

_{Reviews (2): Last reviewed commit: "Scope nullable PHP hydration to from()-b..." | Re-trigger Greptile}