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Date: Wed, 30 May 2007 00:47:47 +0200
Reply-To: Marcus Boerger <helly@php.net>
Message-ID: <95336619.20070530004747@marcus-boerger.de>
To: Emil Ivanov <emil.vladev@gmail.com>
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Subject: Re: [PHP-DEV] function overriding and class inheritance
From: helly@php.net (Marcus Boerger)

Hello Emil,

learn inheritance rules!

And besides PHP follows strict is_a rules.

Even if PHP weren't following strict is_a rules:

Every Work2 is a Work1 so and so any place that uses with Work1 objects
can take Work2 objects. Now "$o->f1($c);" might be using a $o being a
work1 or a work2. That means either f1(C1) or f1(C2). The more general
one is C1. So Work2::f1(C2) must be wrong becasue it no longer accepts
C1. But following is_a rules (even non strict) it needs to. So the code
must be wrong.

If you need a book to understand the rules I could direct you but I don't
recomment reading it really....

best regards
marcus

Wednesday, May 30, 2007, 12:17:20 AM, you wrote:

> Hi,

> I'll try get straight to the point:
> class C1 {}
> class C2 extends C1 {}

> abstract class Work1 {
>  public function f1(C1 $c);
> }

> class Work2 extends Work1 {
>  public function f1(C2 $c);
> }

> Here I get an an error regarding the prototype missmatch.

> Wouldn't it be nice to be able to tighted the requirement - C2 is still C1?

> Regards,
> Emil Ivanov 




Best regards,
 Marcus