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To: Marcus Boerger <helly@php.net>
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	 <868073456.20081231173818@marcus-boerger.de>
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Date: Fri, 02 Jan 2009 19:16:32 +0100
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Subject: Re: [PHP-DEV] [RFC] Re: [PHP-DEV] __invoke() weirdness
From: johannes@php.net (Johannes =?ISO-8859-1?Q?Schl=FCter?=)

Hi,

On Wed, 2008-12-31 at 17:38 +0100, Marcus Boerger wrote:
> So far it is. Yet I as much as you do not like the inconsistency. So I
> spend a little bit on providing the following patch that should do
> what
> you were looking for.

I thought bout this issue for one day or so, there are three things to
consider here:

- the language design question
- implementation-related things
- getting 5.3 out

For the first question I have to say that this is a major change to
language. Bringing this feature in makes it a mixture of a class-based
OO model and JavaScript-like class-less OO model. As I tend to read way
more code than I write I, personally, prefer the clearer class based
approach.

Nonetheless there seems to be large support for this, so let's lake a
deeper look:

> The disadvantage: Calling properties is case sensitive while calling
> methods isn't. But since this has nothign to do with this patch and
> the patch only increases consistency I am all for applying it.

That's one of the symptoms of the underlying problem we're having: In
our object implementation methods and properties are kept completely
separated. Using properties now like methods will have side effects, one
is described above. I found another one today:

<?php
class A {
    public $p;
    public function __construct() {
        $this->p = function() { echo 1; };
    }
}

class B extends A {
    private function p() {
        echo 2;
    }
}

$a = new A();
$b = new B();

$a->p();
$b->p();
?>

What do you expect? Well, the first call, to $a->p(); works, the second
one, to $b->p();, doesn't since where accessing the private method
B::p().

$ sapi/cli/php test.php
1
Fatal error: Call to undefined method B::p() in test.php on line 16

Depending on your view on this that result can be correct or wrong, it
might even be wrong in different ways, maybe overwriting $a->p with
$b->p should be forbidden, maybe it should treat private elements like
non-existent ones.

The obvious thing is that it feels like the "is-a" relationship isn't
enforced anymore.

Additionally there are other areas with such conflicts: Reflection
(ReflectionMethod doesn't work, ReflectionProperty has no hint it's
executable, ...) and other meta-functionality are obvious, others might
(and will) be quite hidden.

I guess the only solid way to implement that feature would be by merging
the property and method tables into an "element" table so we reduce such
conflicts -- while that's a major engine and language change. Every
other approach will have side-effects.

This leads us to the third consideration: 5.3 is around 1.5 years in
development now with lots of new features. It was announced that we
wanted to go to a beta status to get it out soon ("release early,
release often" ...) 

I'd say it would be good to concentrate on making 5.3 stable and then
see how new features are accepted. If users really demand such a
functionality, when using closures for "real life" development, we can
still add it, but that should be done with the time needed to identify
side-effects and other consequences, not in a rush during holiday season
after a feature freeze has been announced.

johannes