Re: [RFC] [VOTE] Deprecations for PHP 8.4

On Tue, Jul 23, 2024, at 4:00 PM, Matthew Weier O'Phinney wrote: >> However, a few people indicated a desire to have an explicit wildcard _ anyway, even if >> it's redundant, as it's a more common and standard approach in other languages. >> We've indicated that we are open to making that an optional secondary vote in the pattern >> matching RFC if there's enough interest (it would be trivial), though I haven't bothered >> to add it to the RFC text yet. >> >> Having _ available could also be used in other "wildcard" or "ignore >> this" cases, like exploding into a list assignment or similar, though I don't believe that >> has been fully explored. > > Can you provide examples of what that usage would look like? And the > question I have really is, does this actually _require_ using "_", or > could another token be used for such matches? Hypothetical pattern matching example: $foo is ['a' => int, 'b' => $b, 'c' => mixed]; That would assert that there's 3 keys. "a" may be any integer (but only an integer), "b" can be anything and will be captured to a variable, and "c" must be defined but we don't care what it is. The suggestion is to basically alias _ to "mixed" for pattern purposes: $foo is ['a' => int, 'b' => $b, 'c' => _]; As "there's a var here but I don't care what it is, ignore it" is a common meaning of _ in other languages. But that would need to be disambiguated from a pattern saying "c must be an instance of the class _". Technically any symbol/set of symbols could be used there (as it's just an alias to mixed, which has the exact same effect), but _ is a common choice in other languages. In theory, that could be expanded in the future to something like (note: this hasn't been seriously discussed that I know of, I'm just spitballing randomly): [$a, $b, _] = explode(':', 'foo:bar:baz'); To assign $a = "foo", $b to "bar", and just ignore "baz". Which might cause parser issues if _ is a legal class name, I'm not sure. There's probably other "ignore this" cases we could come up with, but I haven't actually thought about it. Again, whether any of the above is a compelling argument or not I leave as an exercise for the reader. --Larry Garfield