Memory leak from namespace-level constants in worker mode

[zip-fa]

Version

latest

Steps to Reproduce

1. Install posthog/posthog-php in a Laravel application.
2. Run the application using a long-lived worker runtime (FrankenPHP worker mode, Swoole, RoadRunner, or Laravel Octane).
3. Send requests that trigger PostHog SDK calls (e.g. PostHog::capture(), PostHog::getFeatureFlag()).
4. Monitor memory usage with memory_get_usage() over thousands of requests.

Expected Result

Memory usage should remain stable across requests, since the worker process reuses the same PHP runtime without restarting.

Actual Result

Memory grows linearly with each request and is never reclaimed. The root cause is the namespace-level constants SIZE_LIMIT in lib/Client.php and LONG_SCALE in lib/FeatureFlag.php. In persistent worker runtimes, namespace-level constants are re-evaluated on every request and not garbage-collected between requests, causing a steady memory leak.

Moving these to private const on their respective classes (Client::SIZE_LIMIT, FeatureFlag::LONG_SCALE) ties them to the class autoloader cache, which is loaded once and reused — eliminating the leak.

[ioannisj]

Hey @zip-fa Thanks for the report and the suggested fix!

My investigation found that namespace constants are defined once per process and are not re-evaluated on subsequent requests. So moving them to private const inside a class shouldn't affect memory usage in practice.

Have you actually observed memory pressure going away with that change, or is it more working off an assumption that the constants were being re-evaluated?

[zip-fa]

Hey @zip-fa Thanks for the report and the suggested fix!

My investigation found that namespace constants are defined once per process and are not re-evaluated on subsequent requests. So moving them to private const inside a class shouldn't affect memory usage in practice.

Have you actually observed memory pressure going away with that change, or is it more working off an assumption that the constants were being re-evaluated?

I actually observed a memory leak in php 8.4+symfony in worker mode with frankenphp and i can confirm my fork with the suggested fix works in my env