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Date: Wed, 20 Feb 2008 12:25:29 -0800
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Subject: Re: [PHP-DEV] RFC: Traits for PHP
From: stas@zend.com (Stanislav Malyshev)

Hi!

>   if we go the route of allowing that, then we have to do some protocl
> checks. Meaning if a renamed/aliased method will become an implementation of
> an abstract method then of course it has to be compatible. The beigger

I'm kind of confused on a use case for that. Suppose you have trait TFoo 
that does some API - like implementing serialization, for example. And 
then you have some abstract method bar() that is supposed to do 
something unrelated - like convert pounds to kilograms. And then you 
just rename one of the methods of TFoo into bar() and suddenly it starts 
being used for converting pounds to kilograms just because it has the 
same argument count? I don't see any sane application structure working 
this way. What would be the use case of taking methods from one API and 
using them as implementation for totally unrelated parts of other API? 
What if one of the APIs changes? What if change required to implement 
TFoo but bar() should stay the same? This just looks like very cludgy 
attempt to avoid typing a few extra lines, which will definitely will 
come back to bite the developer in the future. I think this is important 
- to figure out what is the good use case for this.

> dropped or renamed then there is a problem, called missing function. We
> could avoid that easily if we have a compiler that allowed us to check
> which functions are being called. Becasue then we could easily prevent a

We can't - as I already mentioned, call resolution is dynamic in PHP, 
which means compiler can't check which methods are called. On top of 
that, nobody said methods are always to be called on $this with -> 
operator - there are many other ways to call a method on an object.

> In PHP we always allowed all kinds of nasty. We even hesitate to increase

No, we didn't allow all kinds of nasty. PHP never had dynamic method 
addition, dynamic object/class redefinition, etc. even though 
engine-wise it's completely possible. That's the domain of hackish 
extensions like runkit and IMO it should stay there - in it's own closet 
which is clearly labeled "beware of the leopard". I would have no 
objection for runkit to have traits-like functions - in fact, I think it 
can do it right now. Having this in core is another, very different 
business.
-- 
Stanislav Malyshev, Zend Software Architect
stas@zend.com   http://www.zend.com/
(408)253-8829   MSN: stas@zend.com