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To: malone.spencer@gmail.com
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Subject: Re: [PHP-DEV] Pre-RFC proposal: opt-in implicit interfaces /
 structural typing
Date: Sat, 08 Nov 2025 05:45:25 +0000
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From: hanskrentel@yahoo.de (Hans Krentel)



On Friday 07 November 2025 18:05:03 (+01:00), Spencer Malone wrote:

 > Hey all! Long time browser, first time emailer. I wanted to start a 
pre-RFC
 > discussion on the proposal of opt-in implicit interfaces / structural
 > typing / "golang style interfaces".
 >
 > I have an early mostly working POC at
 > 
https://github.com/php/php-src/compare/master...SpencerMalone:php-src:implicit,
 
> and was curious if this was an idea that could get any traction as an 
RFC?
 >
 > For those who don't want to open the link, it's essentially:
 >
 > ```
 > implicit interface Drawable {
 > public function draw(): void;
 > }


If you may be that kind and allow an implicit interface to use a trait...

 >
 > class Circle {
 > public function draw(): void {
 > }
 > }
 >

... then the class could use a trait as well which is then closing the
distance to traits that are not able to full-fill interfaces and their 
using classes,  so the classes can borrow from the traits and both then
somewhat profit from implicit interfaces.

The "innerface" naturally could only use the non-body parts (abstract
parts) of the trait methods / properties, so the copy direction towards
the interface is a reduction to the interface the trait implies.

The trait then can be used in the implicit interface definition to do
both at once (defining an interface and providing an implementation).

 >
 > assert((new Circle()) instanceof Drawable); // This would be true
 > ```
 >

and if I may add, truly great - regardless with or without such
trait reuse.

if it then could work en-par with function defintions (define after
use which currently "explicit" interfaces are not capable of) this
would make it a perfect and modern addition to the language in my
very own eyes.

 > There is some previous art around here in the form of...
 > [...]
 >
 > - Spencer
 >

- h.k.