fix(php): support non-nullable unions

[schani]

PHP generation failed with Error: union are not supported. for any union that isn't just nullable — a heterogeneous array like "mixed": [1, "two", true, null, {"nested": "object"}] made the whole render throw. Nullable unions (?string) already worked; everything else hit seven unimplemented matchType cases.

What this does

• Inline PHP 8.0 union type declarations instead of named union classes: a union property renders as private MixedClass|int|string $v;, its converter parameter as stdClass|int|string (the decoded-JSON side, where classes/maps are stdClass and enums/dates are strings, deduplicated). unionNeedsName is now false — no union class is ever emitted.
• Runtime type dispatch in the from/to/validate converters: an if/elseif chain over the members, most specific check first (instanceof for classes/enums/DateTime, enum-value membership before the plain-string check, is_int before the float check — which also accepts integers, since PHP ints pass wherever floats do), throwing on unmatched values. sample uses the first member; any members act as the catch-all branch.
• PHP reserved words are now forbidden names. The motivating fixture has a property named mixed, whose class used to be emitted as class Mixed — a fatal error in PHP 8 (reserved type name); it's now MixedClass. Previously the renderer protected no reserved word at all, so keys like class or print with object values generated uncompilable PHP. A property named this no longer produces an illegal $this constructor parameter.
• Renderer bugs found by the new fixture coverage are fixed along the way: any/null typed properties are mixed instead of the fatal Object/any/null declarations, the bogus defined() "validation" for any is gone, double validation accepts ints (what json_decode yields for whole numbers), nullable DateTime/UUID declarations keep their ?, nested array/map sample methods are now syntactically valid expressions, empty classes' validate(): bool returns true instead of nothing, and the nullable from converter no longer emits a stray return null; inside map loops.

Testing

quicktype's primary testing method is end-to-end JSON / JSON Schema fixture tests, and this PR is now covered by them (the principle is written down in a new ## Testing section in CLAUDE.md):

• JSON fixture: the PHP whitelist in test/languages.ts grows from 7 easy samples to 18, adding the union-heavy inputs unions.json, union-constructor-clash.json, combinations1–4.json, nst-test-suite.json, kitchen-sink.json, list.json and bug427.json, plus a new test/inputs/json/priority/php-mixed-union.json — the motivating repro ("mixed": [1, "two", true, null, {"nested": "object"}]), which exercises the reserved-word class renaming and union dispatch together. The new input is skipped for the five languages that already skip unions.json (Ruby, Scala 3, Smithy4s, Kotlin, Kotlin Jackson).
• JSON Schema fixture: schema-php is now registered in test/fixtures.ts and runs in CI. 61 of 65 schemas pass; the four skips (with reasons in test/languages.ts) are keyword-unions.schema (PHP class names are case-insensitive, the namer dedups case-sensitively — Java and Python skip it for the same reason), recursive-union-flattening.schema (a top-level union has no named TopLevel class now that unions are inline), top-level-enum.schema (driver-incompatible, as for C#/Ruby) and union.schema (the driver doesn't support top-level arrays).
• Not enabled (pre-existing limitations unrelated to unions): optional-union.json (top-level array), identifiers.json (raw JSON names need comment/string escaping) and keywords.json (the case-insensitive class-name collision above).
• Unit tests in test/unit/php-unions.test.ts stay as a complement: they assert things fixtures can't (e.g. that no union class is emitted) and run without a PHP toolchain.

Both fixtures pass locally end-to-end under a PHP 8.4 CLI (FIXTURE=php script/test: 18/18, FIXTURE=schema-php script/test: 61 schemas), and npm run test:unit passes.

🤖 Generated with Claude Code