On 23/11/2024 20:27, Rob Landers wrote:
Interesting! I actually found it to be intuitive.
Think of it like this:
function increment(array $array) {
$array[0]++;
}
$arr = [0];
increment($arr);
echo $arr[0]; // is 0
We don't expect $arr to be any different outside of the function
because $arr is a value, not a reference.
My mental model, rightly or wrongly, is that passing to a parameter is a
bit like an assignment to a local variable:
function increment(array) {
$array = $__args[0];
$array[0]++;
}
(This is explicitly how subroutine parameters work in Perl; I don't know
if that's affected my mental model, or just means Larry Wall pictured it
the same way.)
You can even assign a new value to it, like any other variable:
function whatever(array $array) {
$array = 'not even an array any more';
}
But in PHP, $this isn't a parameter, and it's never possible to assign a
new value to $this; so it feels completely alien to have a method where
$this stops referring to the current object, and becomes a local variable.
I think it would be clearer to prevent direct modification of $this:
Not that I disagree (see the records RFC), but at that point, why not
make data classes implicitly readonly?
I'm only suggesting restricting mutation on $this, not on the object
itself. $foo->x++ would still work, and have automatic copy-on-write;
but $this->x++ would be an error on a data class, just as $this=$bar is
an error on all existing objects.
That would still be compatible with Ilija's suggestion, which was to
add special "mutating methods":
I actually find this appealing, but it is strange to me to allow this
syntax on classes. Is there precedent for that? Or is there a way we
can do it using "regular looking PHP"; or are structs the way to go?
The way I see it, it's just a third type of method, to add to the two we
already have:
- instance methods: $this refers to the current instance
- static methods: $this is forbidden
- mutating methods: $this refers to the desired result of the mutation
In fact, it's a bit like __construct or __clone, where $this refers to
the newly created/copied object, before anything else points to it.
--
Rowan Tommins
[IMSoP]
