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Date: Mon, 19 Apr 2004 21:10:40 +0300
To: "Sterling Hughes" <sterling@apache.org>,<zeev@zend.com>,
 <internals@lists.php.net>
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Subject: RE: [PHP-DEV] Interface inheritance
From: andi@zend.com (Andi Gutmans)

Yes, but I claim that inheritance is exactly the same thing. I comes with 
an interface which needs to be adhered to. It does tend to be inconsistent 
if we E_ERROR out on interfaces and not on inheritance.

At 09:31 AM 4/19/2004 -0700, Sterling Hughes wrote:
>I agree.  Interfaces are useless if you can't guarantee that a class
>actually implements them.  Violating an interface is violating a contract
>and it should be an compile error - indeed, when coding I mostly rely on not
>properly implementing interfaces to be a compile error.
>
>-Sterling
>
>-----Original Message-----
>From: Zeev Suraski [mailto:zeev@zend.com]
>Sent: Monday, April 19, 2004 1:49 AM
>To: internals@lists.php.net
>Subject: [PHP-DEV] Interface inheritance
>
>All,
>
>Yesterday, someone complained that classes that implement interfaces
>succeed in doing so even when they don't satisfy the prototypes.  While
>this does cause an E_STRICT message to be emitted, it would go unnoticed in
>most cases, as E_STRICT is off by default, in some cases - even when people
>think it's on.
>
>I believe that this behavior is wrong.  I believe that classes should not
>be allowed to say they implement an interface X, unless they actually
>implement all of the methods in that interface with methods that are
>compatible with its prototypes.
>
>Reasoning:
>- Interfaces (and for that matter, abstract classes) are a new feature in
>PHP 5, used solely to enforce implementing classes to abide to the
>prototypes.  There's no issue of downwards compatibility, and there's no
>other use case.
>- Without this, the whole mechanism of class type hints is rendered
>useless.  With it, it gives users the full power of class type hints (and
>instanceof, for that matter) - because they always have the option of
>adding an interface for their base classes.
>
>Suggested behavior:
>Any method that implements (directly or indirectly) an interface method or
>an abstract method, will have implementation checks fully enforced, with an
>E_COMPILE_ERROR emitted in case of an error.
>Behavior for methods that override regular parent methods, that do not have
>interface/abstract prototypes, will not change (E_STRICT message).
>
>Comments welcome - we'd like to sort this out before RC2...
>
>Zeev
>
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