Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:49457
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain zend.com designates 212.25.124.185 as permitted sender)
Message-ID: <7.0.1.0.2.20100819181013.18df1df8@zend.com>
Date: Thu, 19 Aug 2010 18:14:35 +0300
To: "Ionut G. Stan" <ionut.g.stan@gmail.com>
Cc: <internals@lists.php.net>
In-Reply-To: <4C6D39EA.4000705@gmail.com>
References: <4C6CE273.2070501@sugarcrm.com>
 <4C6CE604.1010209@dmi.me.uk>
 <4C6CE793.1020601@sugarcrm.com>
 <1282206735.2561.11.camel@guybrush>
 <4C6CF898.5060706@gmail.com>
 <4C6D2EB8.30700@gmail.com>
 <4C6D39EA.4000705@gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; format=flowed
Subject: Re: [PHP-DEV] inheritance check too strict?
From: zeev@zend.com (Zeev Suraski)

At 17:04 19/08/2010, Ionut G. Stan wrote:
class Parent
>{
>     public function foo(Foo $foo)
>     {}
>}
>
>class Child
>{
>     public function foo(Bar $bar)
>     {}
>}
>
>class Foo
>{}
>
>class Bar extends Foo
>{}
>
>
>
>All fine until here, but what if...
>
>
>
>class Taz extends Foo.
>{}
>
>
>I can't call Child::foo() with an instance of Taz, but I can call 
>Parent::foo() with such an instance. So, I can't use instances of 
>Child wherever instances of Parent would be accepted.

Child should clearly not be allowed to inherit Parent in the code 
above, since the signature of Child::foo() is more restrictive than 
the signature of Parent::foo().  The other way around could work 
(although I don't recall if we allow it):

class Foo {}
class Bar extends Foo {}

class Parent
{
         public function foo(Bar $bar){}
}

class Child extends Parent
{
         public function foo(Foo $foo){}
}


No issues here - since any Bar object is also a Foo object and would 
pass the is_a validation of Foo.  Again, I don't recall if we allow 
such signature overrides or not.

Zeev