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Date: Tue, 6 Dec 2011 14:54:17 +0100
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Subject: One more Liskov Subs. and parameter checking notice
From: jpauli@php.net (jpauli)

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Greetings PHP Intern@ls :)

There is a PHP behavior I disagree with regarding OO model.
It's been here for a long time (5.0 ??, at least 5.2, 5.3 and 5.4) , here
it is :

<?php
interface Iface1 { }
interface Iface2 extends Iface1 { }

class Foo {
    public function bar(Iface1 $arg) { }
}

class Foo2 extends Foo {
    public function bar(Iface2 $arg) { }
}
?>
Strict Standards: Declaration of Foo2::bar() should be compatible with that
of Foo::bar()


I find this wrong.
Liskov (and the error message) says we must stay "compatible" in our
inheritence.
The fact is that we are in the code above :
- A uses IfaceA
- B extends A
- B should be able to overwrite A's method typing their IfaceA params on
IfaceB, if IfaceB extends IfaceA (and is thus compatible with it).

Thoughts ?

Julien.Pauli

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