Draft RFC: foreach iteration of keys without values

This is a new thread for John Bafford's RFC which he mentioned on another thread, see below: https://wiki.php.net/rfc/foreach_void <https://wiki.php.net/rfc/foreach_void> > On Aug 31, 2020, at 5:50 PM, John Bafford <jbafford@zort.net> wrote: > > Hi Riikka, > >> On Aug 31, 2020, at 14:13, Riikka Kalliomäki <riikka.kalliomaki@riimu.net> wrote: >> >> A common pattern that I've seen that could dearly use PHP internal >> optimization, if possible, would be: >> >> foreach (array_keys($array) as $key) { >> } > > I have a draft RFC (https://wiki.php.net/rfc/foreach_void) and patch > (https://github.com/jbafford/php-src/tree/foreachvoid against php 7.0, I think) that helps with > this, by allowing the following syntax: > > foreach($iterable as $key => void) { ... } > > This would iterate over the keys of the iterable, and does not retrieve the values at all. > > In theory, this should be a general performance win any time one needs to iterate over only the > keys of an iterable, because it does not require the use of an O(n) iteration and building of the > array that array_keys() would, plus it works on non-array types (such as generators or iterators). > It also is more performant than foreach($iterable as $key => $_) {}, because it omits the opcode > that instructs the engine to retrieve the value. (Presumably, a future direction could include using > this request to inform generators or iterators to only return keys, and not values, which could > further improve performance, especially if value generation is expensive. But that is out of scope > for this RFC.) > > If this is something we'd like for PHP 8.1 and there are no major objections to the idea, > then after 8.0 is released, I can move the RFC out of Draft and into Under Discussion, and presuming > a vote passes, I'll update the patch as necessary to work against 8.0. But my time is limited > and I'm not willing to put further time into the code unless an RFC vote passes. > > Thoughts anyone? +1 from me. BTW, your RFC says "Next PHP 7.x" for Proposed Version; might need to update that? -Mike