The initial implementation of LogSubscriber in PHPC-2180 maintains a separate global HashTable for registered loggers. This dates back to the original prototype, which used separate add/removeLogger functions, but was retained after modifying the existing add/removeSubscriber methods to handle loggers.

Logging is technically more performant this way since it does not need to filter objects in a HashTable (as is done in phongo_apm_get_subscribers_to_notify); however, that may not be worth the code duplication and additional maintenance. Logging is also not a critical code path.