Allow empty property names

Hi internals, Currently we do not allow (*) creating empty property names on objects, i.e. $obj->{''} = 42; is illegal. While empty property names are unlikely to be useful per se, they are problematic for deserialization of foreign formats like JSON. To avoid this issue {"": null} will currently decode to a property named "_empty_" rather than "". Notably, this means that JSON decode and encode do not round-trip (as we do not convert _empty_ back to an empty name while encoding). There is no technical reason (that I can see) for keeping this arbitrary restriction. I believe that the original reason for the restriction was our use of NUL-prefixed property names for name mangling, combined with the fact that an empty string at the C level happens to "start" with a NUL byte. A patch to drop the restriction and allow empty property names: https://github.com/php/php-src/pull/1836 It does not touch the JSON handling, as there are BC concerns involved there, I leave that to the ext/json maintainer. Any objections to changing this? Regards, Nikita (*) There are roundabout ways to create them anyway.