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Hi everyone
While reviewing the property hooks patch, Bob found a discrepancy in
the implementation and the specification. There is an unfortunate
mistake in one of the examples that suggests specific by-reference
behavior that we did not intend to support.
Specifically, from https://wiki.php.net/rfc/property-hooks#references
(you'll have to scroll down a bit):
```php
class C {
public string $a {
&get {
$b = $this->a;
return $b;
}
}
}
$c = new C();
$c->a = 'beep';
// $c is unchanged.
```
This example implies that the assignment $c->a = 'beep'; will invoke
&get to write to the contents of the reference. However, this is not
the case. Direct assignments will, in the absence of set, fall back
to the builtin write operation for backed properties, or throw for
virtual properties.
Instead of $c->a = 'beep';, the example _should_ have said:
```php
$ref = &$c->a;
$ref = 'beep';
```
Here, $ref = &$c->a; _will_ call &get. What the example
intended
to show is that the reference returned by &get is detached from
$c->a itself.
That said, I did give this idea some thought. I think it would not
have been unreasonable to automatically call &get and assign to the
returned reference when there is a &get hook but _no_ set hook.
However, when trying to implement this, I encountered some technical
issues that make this currently unfeasible. So, we'd like to move
forward with the original semantics: If there is no set hook, then
the assignment will trigger a builtin write for backed properties, or
an error for virtual properties.
If you wish to achieve the behavior described above (using &get to
write to the property), you can implement set to perform the write
to the reference yourself.
I hope that these semantics are acceptable for everyone.
Ilija