Surprising php has a lot of FP aspects.

pas · on Feb 7, 2022

It .. really doesn't. (Sure, probably a tiny bit more than Python.)

It's not static types FP like Haskell/Scala (or even TS), as it just recently started gaining some type safety, and while it had map/reduce call_user_func, it wasn't that big in PHP world.

It simply has/had too much mutability for it, and most PHP practice focused on trying to implement OOP ideas in it in a nice way.

withinboredom · on Feb 7, 2022

FWIW, I don't consider type safety a major issue with FP vs. OOP vs. procedural. I think type safety is just that, a safety net. I've ported things between C#, Scala, and PHP for fun, and regularly find PHP to be more concise due to it's lack of type safety than it being a hinderance. Sure, it sucks that the IDE can't help me out more (lack of generics cough) but static analysis tools really help there, like Psalm and PHPStan. As a side note, Psalm's security scans have pointed out security issues with the original code it was ported from, so that's something...

You can do some pretty fancy things with arrays that you usually only see in FP type languages:

  $arr1 + $arr2 (non-numeric keys) // scala: arr1 ++ arr2
  array_merge($arr1, $arr2) // scala: (arr1 ++ arr2) distinct
  array_unique(array_merge($arr1, $arr2)) // scala: arr1 union arr2
  array_intersect($arr1, $arr2) // scala: arr1 intersect arr2
  array_combine($arr1, $arr2) // scala: arr1 zip arr2
  array_filter(array_map($mapper(...), $arr)) // scala: arr.flatmap(mapper)

in all of these cases, the original array(s) remains untouched. In most OOP languages, the array would probably be mutable (or require some juggling between mutable and immutable types, like C#). That's why its surprising. It's quite verbose in PHP, but the foundations for a FP approach is all there.

What's even more surprising is when performance is comparable to a language like C# on some random benchmarks I've run[1] (opcache + JIT turned on in PHP, C# in "release" optimized compilation). I'd consider it a pretty good contender for serious things.

[1]: https://github.com/withinboredom/distributed-hashmap/blob/23...