Coalesce assign operator (??=) implemented

Hi internals, Some time ago an RFC for the ??= operator has been accepted: https://wiki.php.net/rfc/null_coalesce_equal_operator However, due to implementation difficulties, the RFC hasn't landed since then. I'm happy to say that these difficulties are resolved now, and ??= has landed with https://github.com/php/php-src/commit/a50198d0fef652ca052cda642d6e98a9101eb73f . To summarize the important ??= semantics: $a ??= $b is roughly equivalent to $a ?? ($a = $b). In $a[foo()] ??= bar() the function foo() will be evaluated exactly once, and bar() will be evaluated iff $a[foo()] is null (or unset). Regards, Nikita