PHP has no generics? I read somewhere that is was "too hard" to get right in PHP land, mostly because of how primitive the typesystem is.
Adding generics to PHP would make CS fundamentalists somewhat happy, but do nothing to change the fundamental design of PHP nor offer any of the traditional benefits that generics offer to strongly-typed and compiled languages. And would be a massive headache to implement, while bulking an already heavy VM implementation.
Exactly. The type system was never built for anything even slightly more complex. Its basically annotations for primitive types and classes. PHP has always had an weak type system, so adding generics will most likely never happen.
> Adding generics to PHP would make CS fundamentalists somewhat happy
PHP has really only one collection datatype (the infamous array), so having generics would be tremendously useful, as an example you cant return an typed array from a function, witch is just really bad.
For an counter example, Python managed to do this, while also being a dynamic language, although having a stronger typing than PHP.
PHP chose to check types at runtime. To check that a value is really an array<int> the runtime could have to loop through the entire array. All the types PHP currently implements are simple and cheap to check. For more elaborate cases you need an offline checker like PHPstan and comment-based type annotations. (PHPstan catches 99% of issues before the runtime gets to it so for my own code I'd prefer the Python approach with its cleaner syntax.)
The runtime checking seems the key difference, not so much the historical strength of the type system. Python's language implementation does very little typechecking itself and PHP's third-party offline typecheckers are respectably advanced.
This could be the way PHP could go, they just need the lexer to handle types, and not do any runtime checking at all.
But i guess that goes against what the php devs want, but it sounds so wasteful, to typecheck the same code time after time even if it passed some sort of initial "compile time step".
This subtle difference has huge implications. You could in theory have an "compile step" in. Python, but in PHP you really cant as the program is never "running".
Python built syntax for types / generics etc. Its actually a quite capable typesystem (im not a python developer, but use python on some occasions). Python then has tools for static typechecking that can be run outside execution.
This means that if python would do actual static typechecking on runtime it would be nothing more than wasted cpu cycles.
Thats why python opted for the syntax only, as its basically zero cost. In php land the typechecking is done on EVERY execution, even if the code was unused. (a void functions that has an int param, but gets passed an string, that just discards the parameter). Even worse, a type error thats not executed wont be caught by every execution.
In short PHP typesystem is just runtime checks for primitives / classes and wont catch errors where not executed. Its like the worst of both worlds.
What do you mean by this? The types of variables in PHP >8 are not in comments. Or did I misunderstand something?
Why is it bad?
In particular, why is it worse than not being able to declare a typed array in your current scope? (I understand the basic argument in favor of typed arrays, but I also understand why PHP would choose not to go that route; I'm not sure I see how it's worse to not be able to return one from a function, given that they don't exist elsewhere.)
A even more simpler example is An array of some sort of Item. I cant return array(Item), but i only can return an array.
What is not working?
But that is no different than if you created the array in that scope.
So, again: Why is it "really bad" that you can't return a typed array from a function? What is worse about that than not being able to create a typed array in the current scope?
Also: What, exactly, about that is "not working"? As I said above, I understand the basic arguments about typed arrays; they're conceptually equivalent to weak/dynamic types. And there is value in having strong and static types. But it's hardly a showstopper not to, and PHP works just fine even if you don't use any. It just...makes it easier for us, as programmers, to make mistakes.
So to say it's "not working" simply because it's possible to add elements to the array that don't match the types you want seems like an exaggeration.
Yes array is the evil collection type of everything, but that's how it's meant to work. Array is the quick and dirty 'throw everything in there' thing. PHP has classes and they're very full featured and offer lots of type safety - use those.
LOL, no its not. PHP has an weak type system, while python is strong. Both are dynamic.
$sum = 10 + "50"; // 60 in PHP
sum = 10 + "50" // TypeError in pythonAlso, you can just flip on strict typing in PHP, and you should know that.
Really, that's probably enough for a lot of cases, because PHP doesn't have operator overloading. Yes, you can add '10' + 10 and get 20, but not if either of those go into any function. If you have a function that needs to do string stuff, you take string stuff in, and you don't have to worry about string operations or coercing ints or anything.
TLDR: The PHP compiler isn't really suited for the job, it would introduce a lot of complexity to an already complex codebase and the memory/performance hit would be substantial.