Re: [PHP-DEV] Class Extension

First, my apologies to the readers. Something is chewing up my formatting and indenting. I’m still trying to figure out a cause.

If we ignore implementation details and ownership it's pretty similar to what we have with traits. In PHP, what would be the benefit of extensions over traits? One thing that comes to my mind is that traits can be used by whatever chooses to add it (back to ownership). Good one, but what else? If ownership is the only concern then maybe a small addition to traits could achieve the same?


```
trait Foo
{
    for Baz\Bar::class;  // inverse of "use" to limit usage
}

class Bar
{
    use Foo;
}
```

Brings conflict resolution for free; and I think it would be cheaper than yet another class-like thing. Maybe also feels more php-ish since we already have the trait concept?

If we ignore precise syntax and implementation, this is exactly the mental model of my RFCs and implementations. It is applying a trait to an existing class that you don’t control.

The similarities don’t end there. This is the same infrastructure as what is used to implement this feature.

The reason I don’t feel the `trait … for` syntax is appropriate is because of `$this`. In a function inside a typical trait, `$this` refers to an instance of the trait. In an extension, `$this` refers to an instance of the class being extended. Adding the `for` block to the trait changes the type of `$this` in the entire trait. That is unintuitive and likely to introduce barriers to understanding.


Holly