Add benchmarks and micro-optimise the injection hot path

[TomA-R]

Summary

Applies four micro-optimisations to the injection hot path, all with passing tests and PHPStan level 6 clean

Benchmark setup

23 injectable fixture classes across three groups (no-constructor, 2-dep, 3–4-dep) backed by 20 pre-registered Pimple singletons. Total ~744 injections per simulated request.

Run with:

php benchmarks/bench.php [--requests N]

Three reported sections:

1. Cold path — first injection per class (reflection + cache population)
2. Warm path — subsequent injections with hot caches (steady-state throughput)
3. Request simulation — fresh injector per repetition, reports min/median/mean/p95/max

Optimisations

#	Location	Change
1	Injector::create()	Check empty($parameters) in create() itself and call buildParameterArrayFromContainer() directly, skipping the buildParameterArray() wrapper call on the common autowiring path
2	Injector::buildParameterArrayFromContainer()	Drop $position key tracking — signature arrays are always 0-indexed sequential, so $parameters[] is equivalent and avoids keyed iteration overhead
3	CachingClassInspector	Replace $constructorCache[$class] = [$result] wrapper trick with two arrays ($constructorCached presence flag + $constructorSignatures values), keeping the fast isset() check while removing the [0] offset dereference on every cache hit
4	Injector::$containerHasCache	Cache container->has($type) results per FQCN — the container is sealed at bootstrap so this eliminates a PSR-11 method call + Pimple hash lookup on every repeated injection sharing the same container-registered dep types

Results (PHP 8.4, OPcache off, 744 injections/request)

Metric	Before	After	Δ
Warm throughput	413k ops/s	731k ops/s	+77%
Avg time per request	1.40 ms	1.01 ms	−28%
Request sim throughput	530k ops/s	733k ops/s	+38%

Test plan

• ./vendor/bin/phpunit — 86 tests, 145 assertions pass
• ./vendor/bin/phpstan analyse — no errors
• php benchmarks/bench.php --requests 50 — runs cleanly, inspect throughput numbers

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