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Date: Thu, 26 Feb 2015 23:15:49 +0200
Message-ID: <dd5923743d74f95199f5858a71f7cf0c@mail.gmail.com>
To: Mike Willbanks <pencap@gmail.com>
Cc: PHP Internals <internals@lists.php.net>
Content-Type: text/plain; charset=UTF-8
Subject: RE: [PHP-DEV] A different user perspective on scalar type declarations
From: zeev@zend.com (Zeev Suraski)

> -----Original Message-----
> From: Mike Willbanks [mailto:pencap@gmail.com]
> Sent: Thursday, February 26, 2015 10:43 PM
> To: Zeev Suraski
> Cc: PHP Internals
> Subject: Re: [PHP-DEV] A different user perspective on scalar type
> declarations
>
> Here is the most basic example and something that people are going to
> often
> run into.  You see this type of code with hydrators, mappers, etc.
> Ultimately
> the end result is going to be the same:
>
> https://gist.github.com/mwillbanks/04e3be68f737c25984ab
>
> I'm not certain if there is a need to explain that bit a bit more.  But a
> string
> "1" as a bool should work as with a string "0".  For instance, today we
> have
> the following for both string's 0 and 1:
>
> $bool = "0";
>
> var_dump($bool); // "0""
>
> var_dump($bool == false); // true
> var_dump($bool == true); // false
> var_dump($bool == 0); // true
> var_dump($bool == 1); // false

OK, so essentially you're saying that you expect "1" and "0" to be coerced
into booleans.  This is something we've been wondering about in the Coercive
RFC, and in the original version we allowed all scalars to be coerced into
bool - but not the other way around.  Right now the RFC only allows for
integer->bool coercion, but the database use case seems to be a pretty
strong one.  The options we considered were int only, int+string or none at
all.  Float is the one that really stands out as pretty meaningless.

I think the opposite side is a lot trickier - converting from bool into
string (or any other scalar type for that matter) is quite likely to hide
bugs.  We've found a bunch of bugs like that today, where return values of
strpos() are fed without validation into other APIs that expect an offset,
and similar use cases.  Such code patterns are bound to be hiding bugs, at
least in some cases.  I'm guessing that direction is less of an issue in
your mind, correct?

Zeev