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Date: Wed, 30 Apr 2008 13:21:26 -0500
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To: Nathan Nobbe <quickshiftin@gmail.com>
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Subject: Re: [PHP-DEV] why interfaces ?
From: jeremy@omegavortex.net (Jeremy Privett)

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Nathan Nobbe wrote:
> On Wed, Apr 30, 2008 at 12:06 PM, Jeremy Privett <jeremy@omegavortex.net>
> wrote:
>
>   
>> Nathan Nobbe wrote:
>>
>>     
>>> all,
>>>
>>> in recent weeks there has been a lot of arguing about what interfaces are,
>>> arent (on php-general and now on the internals list as well) etc. etc.
>>>
>>> i am quite curious, why interfaces were added to the language in the first
>>> place.  note, i am not criticizing them, i am overjoyed that the language
>>> has them, however i am curious about the history.  is this something php
>>> borrowed from java?  does it have anything to do with 'entirely virtual
>>> classes' in c++ ?  i think that the history behind the addition of
>>> interfaces to php, would shed a lot of light on their intended purpose for
>>> use by php developers.
>>>
>>> thanks,
>>>
>>> -nathan
>>>
>>>
>>>
>>>       
>> "Interfaces" exist in different OO-enabled languages. PHP strengthened its
>> object model in PHP 5, and thus the introduction of interfaces. I'm pretty
>> sure the intended purpose of interfaces was just like pretty much every
>> other language. You implement interfaces in order to provide a consistent
>> API. As long as class A implements interface B, I can be for certain that
>> it's going to contain methods C and D. Interfaces also give you the ability
>> to "type hint" against them, requiring objects that implement that
>> interface, thus ensuring you know what methods are on that object.
>>
>> Interfaces are a very powerful feature, when implemented properly.
>>     
>
>
> thank you for you response Jeremy.  i understand what interfaces are and i
> have stressed their importance and power on php-general more than once.  im
> just curious more about what influenced the addition of them to php.  im not
> as old as many of them members in the community, so i know there are many
> people who have dealt with more languages than i on a daily basis during
> their careers.  from my limited base of knowledge, i think java was the
> first language to add the keyword 'interface'.  and my presumption is that
> that grew from the convention of creating 'interfaces' in c++ by writing
> entirely virtual classes (as mentioned in gang of four).  i have heard
> different perspectives on this, but i figured, what better place to get to
> the bottom of it than to ask the people who decided to add the interface
> construct to php in the first place.
>
> -nathan
>
>   

Absolutely. I vaguely remember the discussion on php-general, though I 
don't think I participated. I think Java was the first language to 
implement the keyword, but the concept has definitely been around since 
C++. If I had to guess, the reasoning was probably that it felt a 
natural part of the object model, possibly influenced from Java. The 
whole reason I asked the other question previously about the properties 
in interfaces is because I've been working in C# lately, and it allows 
implementing properties in interfaces. I never needed the functionality 
before, but now that I've actually used it in another language, I've 
found a use-case for it and attempted in PHP only to find that it 
resulted in a fatal error. Thus, the inquiry to php-internals.

-- 
Jeremy Privett
C.E.O. & C.S.A.
Omega Vortex Corporation

http://www.omegavortex.net

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