Summary

Fixes #2340

Raises the minimum PHP version across the monorepo from 7.2 to 7.4, drops the two now-stale CI legs, retires workarounds whose comments invited removal at this bump, and opportunistically modernizes plugin source to use PHP 7.4 typed properties and arrow functions.

Floor bump

• composer.json: require.php and config.platform.php → ^7.4 || ^8.0 / 7.4.
• tools/phpcs/phpcs.ruleset.xml: testVersion → 7.4-.
• All ten plugin bootstrap headers: Requires PHP: 7.4.
• .github/workflows/php-test-plugins.yml: drops 7.2 and 7.3 from the unit-test matrix.
• CONTRIBUTING.md, AGENTS.md, phpstan.neon.dist comment updated to reference 7.4.

Retired workarounds

• OD_Link_Collection::get_prepared_links() — drops the empty-input guard around array_merge( ...array_map( ... ) ) that PHP 7.2/7.3 needed.
• plugins/speculation-rules/settings.php — heredoc closer is reindented to its enclosing block using PHP 7.3+ flexible heredoc syntax.

Modernization

• Native typed properties added across all 10 plugins (~60 properties across 24 classes); @var docblocks retained where they carry PHPStan-level subtypes (non-empty-string, int<1, max>, array shapes, etc.) the native type can't express.
• A handful of bool|string, bool|callable, int|float|null properties stay un-typed with inline phpcs:ignore + a TODO note pointing at the eventual PHP 8.0 floor bump (PHP 7.4 has no native union types and callable is not allowed as a property type).
• Lazy-init properties (is_array($prop) sentinel) refactored to ?T + null === $prop.
• tools/phpcs/phpcs.ruleset.xml: removed the enableNativeTypeHint=false suppression so the SlevomatCodingStandard PropertyTypeHint sniff now requires native types in source; also excluded UselessAnnotation (so it doesn't fight WPCS's required @var) and MissingNativeTypeHint for tests (matching how other strict sniffs are already excluded for plugins/*/tests/**).
• ~10 single-expression closures converted to arrow functions in OD, performance-lab, image-prioritizer, speculation-rules, web-worker-offloading, and view-transitions.

The PR is structured as 30 small logical commits so review and bisection stay easy.

Test plan

• CI: php-test-plugins matrix shows three base legs (8.1, 8.0, 7.4) instead of five
• CI: php-lint, plugin-check, and PHPStan green
• Local: composer install resolves without re-locking
• Local: composer phpstan (level 8) green
• Local: composer lint:all green
• Local: npm run test-php passes the 10 plugin suites
• Manual: activate Optimization Detective and Speculative Loading on a wp-env'd site and confirm the link-collection path and the speculation-rules admin notice still render correctly

I fed this issue into Claude Code with the prompt:

I want to update this repo from the PHP 7.2 requirement to PHP 7.4. For reference, see this GitHub issue: #2340

In plan mode, it came up with the following:

Bump Performance plugin monorepo minimum PHP from 7.2 → 7.4

Context

The Performance Team's repo currently requires PHP 7.2, but tracking issue
#2340 calls for moving the floor to PHP 7.4. WordPress
core's own minimum has already moved past 7.2, so the older floor is buying
nothing in compatibility while costing two CI matrix jobs and blocking use of
typed properties, arrow functions, and the ??= operator.

This plan does the floor bump end-to-end: configuration, plugin headers, CI
matrix, lint/static-analysis settings, and docs; removes two now-dead
workarounds whose comments explicitly invite their removal at this version
bump; and opportunistically modernizes the codebase by converting class
properties (well-documented via @var) to native PHP 7.4 typed properties and
collapsing single-expression closures into arrow functions where the
conversion is unambiguous.

The user has approved an opportunistic modernization pass (not just a
config-only bump), so the plan covers both the version bump and the followup
typing work in a single PR.

Phase 1 — Bump the floor (config, headers, CI, docs)

composer.json

• Line 15: "php": "^7.2 || ^8.0" → "php": "^7.4 || ^8.0"
• Line 46 (config.platform): "php": "7.2" → "php": "7.4"

tools/phpcs/phpcs.ruleset.xml

• Line 6: <config name="testVersion" value="7.2-"/> → value="7.4-"
• Line 118: delete the <property name="enableNativeTypeHint" value="false" /><!-- Only available in PHP 7.4+ --> line so the SlevomatCodingStandard PropertyTypeHint sniff defaults back to requiring native type hints. (See Phase 4 — every class property must gain a native type before this gate is allowed to be the default; the conversion lands in the same PR.)

phpstan.neon.dist

• Line 16 comment: change "config.platform.php being 7.2" → "config.platform.php being 7.4". The phpstan/php-8-stubs scan entries below still apply (those are PHP 8.0 polyfills — the polyfill need is unrelated to the 7.4 floor).

Plugin bootstrap headers — Requires PHP: 7.2 → Requires PHP: 7.4

• plugins/auto-sizes/auto-sizes.php:7
• plugins/dominant-color-images/load.php:7
• plugins/embed-optimizer/load.php:7
• plugins/image-prioritizer/load.php:7
• plugins/optimization-detective/load.php:7
• plugins/performance-lab/load.php:7
• plugins/speculation-rules/load.php:7
• plugins/view-transitions/view-transitions.php:7
• plugins/web-worker-offloading/load.php:7
• plugins/webp-uploads/load.php:7

.github/workflows/php-test-plugins.yml

• Line 42: php: ['8.1', '8.0', '7.4', '7.3', '7.2'] → php: ['8.1', '8.0', '7.4'] (drops the two unit-testing jobs the issue calls out). Leave the include: block alone — the existing php: '7.4' + wp: '6.6' and 8.2/8.3/8.4/8.5 trunk entries stay.

Documentation

• CONTRIBUTING.md:10: "minimum required version right now is 7.2" → "7.4".
• AGENTS.md:83: "backward compatible with PHP 7.2" → "PHP 7.4".

Out of scope for Phase 1

• plugins/*/readme.txt files have no Requires PHP header (it's pulled from the .php bootstrap by w.org), so no readme.txt changes needed.
• No per-plugin composer.json files exist; only the root one.
• The package.xml at the repo root is an untracked Xdebug PECL manifest unrelated to this work; ignore.

Phase 2 — Remove dead 7.2/7.3 workarounds

Both call sites carry comments that explicitly say the workaround can be retired at the bump.

plugins/optimization-detective/class-od-link-collection.php (around line 130-135)

PHP 7.4 changed array_merge() to allow zero arguments, so the empty-input guard is no longer required. Remove the if ( count( $links_by_rel ) === 0 ) { return array(); } block and the explanatory comment; let the existing array_merge( ...array_map( ... ) ) call run unconditionally.

plugins/speculation-rules/settings.php (around line 343-344)

PHP 7.3 introduced flexible heredoc/nowdoc indentation. Re-indent the closing JS; marker to match its enclosing block (two more levels in) and delete the // 👆 This 'JS;' line can only be indented two tabs when minimum PHP version is increased to 7.3+. comment. Also re-indent the heredoc body so it lines up with the new closer (PHP 7.3+ strips the closer's indentation from each line uniformly).

Optimization-detective changelog note

The plugins/optimization-detective/readme.txt:263 line "Use PHP 7.2 features in Optimization Detective" is historical changelog content and should be left alone.

Phase 3 — Modernization: typed properties

The Slevomat PropertyTypeHint sniff is being un-suppressed in Phase 1, so every class property in non-test plugin code must gain a native type hint in this PR. The good news from the inventory: 63 of 64 properties already carry single-type @var docblocks, so this is mechanical.

Approach per property

1. Read the existing @var T docblock.
2. If T is string, int, bool, float, array, self, a class name, or T|null (which becomes ?T), declare it natively: private ?string $foo; or private array $bar = array();.
3. If T is a non-null union beyond T|null (e.g., array|false, string|int) — PHP 7.4 doesn't support these natively; refactor the property to use a single type plus a default that signals the absence (e.g., empty array, 0), or leave the property untyped and add an inline phpcs:ignore for that one property with a TODO: PHP 8.0 note. Inventory found ~11 such properties — handle them one-by-one in the diff, preferring refactor over suppression where the codepath cleanly allows it.
4. Initialize at declaration where the type requires it (PHP 7.4 throws on read-before-write of typed uninitialized non-nullable properties). Use the existing constructor's initial value as the literal.
5. Keep the @var docblock — it stays valuable for PHPStan-level subtypes (e.g., non-empty-string, array shapes) that the native type can't express.

Files in scope (28 classes, 64 properties)

Heaviest: optimization-detective (16 classes, 45 props). Top conversion targets:

• plugins/optimization-detective/class-od-html-tag-processor.php — 9 properties
• plugins/optimization-detective/class-od-url-metric-group.php — 7 properties
• plugins/optimization-detective/class-od-url-metric-group-collection.php — 6 properties
• plugins/optimization-detective/class-od-tag-visitor-context.php — 5 properties
• plugins/optimization-detective/class-od-template-optimization-context.php — 5 properties
• Remaining od-* classes, class-od-element.php, class-od-data-validation-exception.php, class-od-link-collection.php, class-od-strict-url-metric.php, class-od-tag-visitor-registry.php, class-od-url-metric.php, class-od-visited-tag-state.php, storage/class-od-storage-lock.php, etc.

Other plugins:

• view-transitions — 2 classes, 9 properties
• performance-lab — 2 classes, 5 properties
• image-prioritizer — 4 classes, 3 properties
• embed-optimizer — class-embed-optimizer-tag-visitor.php — 1 property
• speculation-rules — 1 class, 1 property
• dominant-color-images — no class properties to convert

The 1 property lacking an @var (uncovered by the inventory) gets typed by reading its assignments in context.

Phase 4 — Modernization: arrow functions

Convert single-expression closures function (...) { return <expr>; } to fn (...) => <expr> where:

• The body is a single return statement (no other statements, no nested closures).
• No use ($x) clause is needed (arrow functions auto-capture by value, which is a behavior change only when the closure currently captures a reference).
• The closure isn't static function already in a context where staticness matters — static fn is allowed in PHP 7.4 and should be kept.

Highest-density files (from inventory):

• plugins/performance-lab/ — ~18 closure call sites across ~9 files
• plugins/optimization-detective/ — ~15 across ~8 files (notably storage/data.php, helper.php, optimization.php)
• plugins/image-prioritizer/, plugins/speculation-rules/ — a handful each

Estimate ~15–25 conversions across the repo. Inspect each individually rather than mechanically — leave multi-statement closures untouched.

The ??= operator: 0 candidates found in the codebase. No work.

Commit strategy

Each discrete change lands in its own logical commit, in this order, on the update/php-74 branch:

1. Bump composer.json PHP requirement to ^7.4 || ^8.0 — require.php and config.platform.php. Run composer update --lock only if the lock file legitimately changes; otherwise omit.
2. Bump phpcs testVersion to 7.4- — single edit in tools/phpcs/phpcs.ruleset.xml line 6.
3. Bump plugin header Requires PHP to 7.4 — all 10 plugin bootstrap files in one commit (single mechanical change across the monorepo).
4. Drop PHP 7.2 and 7.3 from CI unit-test matrix — .github/workflows/php-test-plugins.yml.
5. Update CONTRIBUTING.md and AGENTS.md to reference PHP 7.4 — docs only.
6. Update phpstan.neon.dist comment to reference 7.4 — single comment line.
7. Remove PHP 7.2/7.3 array_merge empty-input workaround — plugins/optimization-detective/class-od-link-collection.php. (Phase 2.)
8. Re-indent speculation-rules heredoc closer for PHP 7.3+ flexible heredoc — plugins/speculation-rules/settings.php. (Phase 2.)
9. Convert optimization-detective class properties to native typed properties — one commit per class file, or one bundled commit for all od-* classes if the diff stays reviewable. Target: each class's typed-property conversion in its own commit so blame stays clean. (Phase 3.)
10. Convert remaining plugin class properties to native typed properties — view-transitions, performance-lab, image-prioritizer, embed-optimizer, speculation-rules. One commit per plugin.
11. Re-enable Slevomat PropertyTypeHint native type requirement — remove the enableNativeTypeHint=false line from tools/phpcs/phpcs.ruleset.xml. This commit must come after all property typing is in place; ordering it last in the typing-related commits keeps composer lint:all green at every commit.
12. Convert single-expression closures to arrow functions — one commit per plugin (or per file if a plugin has many). (Phase 4.)

Commit messages follow the existing repo style (imperative present tense, no Anthropic Co-Authored-By trailer unless requested). Group order ensures bisection: every commit leaves the repo in a working, lint-green state.

Defer commit creation until the user explicitly asks to commit; per CLAUDE.md guidance, do not auto-commit.

Phase 5 — Verification

Run locally before opening the PR:

1. composer install — confirms platform/require change parses.
2. composer phpstan — must stay green at level 8.
3. composer lint:all — must stay green; verifies the enableNativeTypeHint removal is satisfied (i.e., every property gained its native type).
4. npm run test:php — full PHPUnit suite. Expect any test that exercises the array_merge empty-input branch in optimization-detective to still pass (the unconditional array_merge returns the same array() for empty input on PHP 7.4+).
5. composer test:plugins — per-plugin suites.
6. npm run env:cli -- plugin activate optimization-detective speculation-rules — sanity-check on the wp-env'd WordPress that the two files we edited still load (heredoc reformat in particular).
7. Optionally bring up the dev environment (http://localhost:8000/) and visit the front-end to confirm Optimization Detective's link collection and Speculation Rules' admin notice render correctly.

CI verification once pushed:

• php-test-plugins.yml should now show 3 base-matrix jobs (8.1, 8.0, 7.4) instead of 5 — confirms the matrix change took effect.
• php-lint.yml should pass on latest PHP.
• plugin-check.yml should pass on PHP 8.3.

Critical files (for quick navigation during execution)