Maybe just a wee bit late to ask this question, but shouldn't we have long since changed `#define ZEND_ENGINE_3` to `#degine ZEND_ENGINE_4` ?
Was that deliberate since (unlike with 4->5 and 5->7) the engine's API surface area hasn't skewed so bad? I ask because ZEND_VERSION did get updated to the 4.x.x series. -Sara
