Re: [Concept] Flip relative function lookup order (global, then local)

On Tue, Aug 20, 2024 at 11:34 PM Ilija Tovilo <tovilo.ilija@gmail.com> wrote: > Hi Levi > > On Tue, Aug 20, 2024 at 5:14 PM Levi Morrison > <levi.morrison@datadoghq.com> wrote: > > > > I have long been in favor of a larger BC break with better language > > consistency. Class lookup and function lookup with respect to > > namespaces should be treated the same. The difficulty is getting a > > majority of people to vote yes for this. Keep in mind that qualifying > > every global function is annoying but probably can be somewhat > > automated, and will bring better performance. So again, this improves > > the existing code even without upgrading. > > > > Yes, there would be complaints about it. Yes, there are probably some > > people or projects who wouldn't upgrade. I don't particularly care, as > > there are increasingly more operating systems and companies providing > > LTS support for long periods of time. Probably Zend.com will offer LTS > > support for the last PHP 8.X release, and possibly there will be some > > distro which also has it. I believe it's the right thing to do > > because: > > > > 1. It's faster. > > 2. It enables function autoloading in a similar manner to class > autoloading. > > 3. It's more consistent, and simpler to teach and maintain. > > > > It's rare that you get all of these together, often you have to make > > tradeoffs within them. > > The approach I originally proposed also solves 1. and 2. (mostly) with > very little backwards incompatibility. Consistency is absolutely > something to strive for, but not at the cost of breaking most PHP > code. > > To clarify on 2.: The main issue with function autoloading today is > that the engine needs to trigger the autoloader for every unqualified > call to global functions, given that the autoloader might declare the > function in local scope. As most unqualified calls are global calls, > this adds a huge amount of overhead. > > Gina solved this in part by aliasing the local function to the global > one after the first lookup. However, that still means that the > autoloader will trigger for every new namespace the function is called > in, and will also pollute the function table. > > Reversing the lookup order once again avoids local lookup when calling > global functions in local scope, which also means dodging the > autoloader. The caveat is that calling local functions in local scope > triggers the autoloader on first encounter, but at least it can be > marked as undeclared in the symbol table once, instead of in every > namespace, which also means triggering the autoloader only once. > > Ilija > Hi, I completely agree with Levi's perspective, aligning class and function lookup with respect to namespaces seems a very sensible option. It will improve consistency and pave the road for autoloading functions without quirks. The impact of fixing functions look up is overstated. For instance, PHP-CS-Fixer can add "global namespace qualifiers" to all global functions in a matter of minutes, it is not like people have to go through code and change it manually. To ease the transition, PHP can ship a small fixer with the next PHP version for changing global function usage (prepending \ or adding use statements) and be done with the inconsistency once and for all. Kind regards, Faizan