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Date: Sat, 22 May 2010 19:50:28 +0300
To: Josh Davis <phpwnd@gmail.com>
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Subject: Re: [PHP-DEV] Type hinting
From: zeev@zend.com (Zeev Suraski)

At 19:30 22/05/2010, Josh Davis wrote:
>On 22 May 2010 17:04, Zeev Suraski <zeev@zend.com> wrote:
> > As one of the key people who designed PHP's type system I consider strict
> > type checks completely alien to and counterintuitive in PHP and 
> am therefore
> > pushing to implement 'weak' typing instead, in a way that's consistent and
> > familiar to users.
>
>I would normally refrain from posting on the dev list but as a "user"
>I feel the need to make sure that my position isn't misrepresented, so
>here it is.

I think that users' opinion about language direction is very 
important, so thanks for writing.

>As you wrote, you worked on PHP's _type system_ which is dynamic,
>really cool, juggles strings with ints and what not. However, the
>topic here is the _type hinting system_.

Well I actually wrote PHP's type hinting system too :)  And it's no 
coincidence there are no type hints for scalars, and that stems 
directly from PHP's type system.  As a part of introducing type hints 
to PHP back in 2003, there was a discussion about whether or not to 
add scalar type hints.  Consensus was against it, and actually as a 
part of the agreement to add type hints to PHP - we agreed we'll 
'never' introduce scalar type hints because of the baggage and 
inconsistency it comes with.  Never is not a very long time when it 
comes to software though...

>As far as I know, there's no
>"weak" type hinting; if a method signature hints for an array and is
>given an integer, it throws a catchable fatal error. Therefore, as a
>user, what I am familiar to is a strict _type hinting system_.
>Anything else would feel inconsistent to me.


That's true, but then, there's also no way to auto-convert class Foo 
to class Bar - while there is a way to auto-convert between scalar 
types in many (if not most) cases.
Consider a simple example - class Child extends Parent {}  strict 
type hinting is the equivalent of not allowing an object of class 
Child when a function expects an object of class Parent.  Much like 
Child is_a Parent, "123" is_a int.

Zeev