[RFC] anti-coalescing-operator

Since PHP 7.0 brought forward the Null Coalescing Operator (??), writing more succinct code for how to handle null values has been a blessing. But, what about the inverse when you want to do something when a value is not null? You're left with the traditional (and sometimes verbose) methods of using if conditions or the full-blown ternary operator `$foo !== null ? <something> : null;`. I am here to gauge the interest of the community in having an anti-coalescing operator that would execute code only if the condition is not null, otherwise returning null in its stead. If this is not a wholly terrible idea, I will -- as suggested -- then continue to create an official RFC. My initial thought process would be to use a similar syntax to the Null Coalescing Operator (??), but to add negation: `$bar = $foo !?? $foo->getBar(). I didn't want to use !?` because then if anybody wanted to add an anti-ternary operator (e.g., !?:) for falsey comparison, then they'd have to get creative or use the three-character approach I am already proposing. The purpose is simply to negate the existing behavior, so at first glance I do not see any BC breakages or additional complexities that haven't already been addressed - naturally, I could be wrong. The driving use case, as hinted at in my above example, is if I have a nullable object I only want to call a method on it if the object is not null. Otherwise, default to the null value. I am working through the RFC Howto [https://wiki.php.net/rfc/howto], and it suggests that I ask for wiki karma for my account (897syudjhf) so that I may create the RFC when appropriate. Additionally, I have not [yet] found any existing precedence for anti-coalescing; i.e., there does not seem to be an elegant counterpart to COALESCE() in SQL. And, as they say, naming is hard. If anti-coalescing-operator does not sit well with you all, I am open to naming suggestions. Thank you for your time, Ken Stanley