[php-src] Issue #8437: WeakMap::offsetExists return false if value is null

Issue: https://github.com/php/php-src/issues/8437 Comment Author: cmb69 > Despite the confusing name, the API contract of offsetExists is that it must return false for > null values. It is the analogue of __isset() and must match > isset() semantics. Ah, right. > Will other Spl implementations of ArrayAccess, like SplObjectStorage, will change in the future > according to this? SplObjectStorage::offsetExists() is an alias of ::contains(), what is apparently a deliberate design decision: https://github.com/php/php-src/blob/7ce5e0a8f166142f64edfc2cd1f92c45b9c0b946/ext/spl/spl_observer.c#L459 I think we should clarify the respective note in the manual. Are there other classes, where ::offsetExists() exhibits this behavior?