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Date: Wed, 25 May 2016 14:37:08 -0700
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Subject: Re: [PHP-DEV] [RFC][Vote] Typed Properties
From: smalyshev@gmail.com (Stanislav Malyshev)

Hi!

> We already have the differentiation between IS_NULL and IS_UNDEF, why
> not expose the latter to userland? I mean, JavaScript has it too and
> people are able to understand it.

IS_UNDEF is not a PHP type, it is an engine implementation flag. Now,
adding a new type "undefined" would be a pretty big thing and then you'd
need to deal with all the implications of it. Including a huge BC break
of changing the type of all uninitialized variables, and the question of
"what if I want my parameter to be able to accept undefined values" and
so on. Huge can of worms, and all of it again just to have a type that
is exactly like null but not null. While the only reason null exists is
to do exactly what "undefined" is proposed to do.

-- 
Stas Malyshev
smalyshev@gmail.com