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Date: Fri, 15 Apr 2016 09:52:51 +1000
Cc: Davey Shafik <davey@php.net>,
 PHP internals <internals@lists.php.net>
Message-ID: <04125064-C4C4-43C1-8EC0-8CD633E3A0F2@simon.geek.nz>
References: <CAESVnVoFQUe7g4DGkszG2gR3gT3EhwEe=+CaUksUcRp0metR2A@mail.gmail.com> <CANaX5nfHZGKwqO=1fvYBoEJjqceLX99FsWheQzH3=cbE5-UW5w@mail.gmail.com> <CAESVnVpHfkb6yexNN2mZz3Dqv-_4S+yUoyba1Hm+S45NGH+cAg@mail.gmail.com>
To: Sara Golemon <pollita@php.net>
Subject: Re: [PHP-DEV] Interpolation using ${} syntax with spaces inside the braces
From: simon@simon.geek.nz (Simon Welsh)

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> On 15/04/2016, at 9:40 AM, Sara Golemon <pollita@php.net> wrote:
>=20
> On Thu, Apr 14, 2016 at 3:37 AM, Davey Shafik <davey@php.net> wrote:
>> Whitespace inside of { } should not matter, the contents should be =
evaluated
>> as an expression and it's results used to determine the variable =
name, so
>> ${great} should also be $my as in the other cases.
>>=20
> Right.  Which is why I'm conflicted on bug/not-bug/different-bug.
>=20
> IMO, the label inside ${...} should either always be a variable name
> (like HHVM handles it), or always be an expression.  What we have is
> "It's always an expression except in the one specific case of it being
> a valid variable name, in which case that takes precedence.  Since the
> versions containing spaces aren't valid variable names, they fall back
> on the more general expression handling.
>=20
> So I'd be inclined to say "That exception to the rule is the problem",
> except that this is variable interpolation behavior that goes ALL THE
> WAY BACK, and I wouldn't break BC for the world.
>=20
> So the question becomes: What's the right move going forward.  My
> inclination would be to either:
> A: Ignore surrounding whitespace within the ${...} expression.
> Essentially, adopt HHVM's output for these examples.
> B: Throw an error on surrounding whitespace.  This will make
> discovering timebombs like these in existing code easier to catch.
>=20
> In either case, if the programmer actually did want the
> constant->variable double-interpolation, that could be easily achieved
> via "${(foo)}" which disambiguated foo as a variable name from foo as
> an expression.
>=20
> -Sara
>=20
>> Is this related to the use of quotes around string array keys inside
>> strings?
>>=20
>> e.g. "$foo[great]" does not evaluate to $foo['my'] but to =
$foo['great'].
>>=20
> I don't think so... I have a feeling that's yet another weird oddity
> to PHP parsing that's waiting to bite us in new and surprising ways.
>=20
> -Sara

When not inside a string, the inside of the ${...} is always treated as =
an
expression, by both PHP and HHVM (https://3v4l.org/i2kOP), so that looks =
like the
=E2=80=9Ccorrect=E2=80=9D handling for inside a string.

There is also differing behaviour in PHP when using array access, =
depending on if
the label starts with a space or not (https://3v4l.org/YPXkr). This =
behaviour is
inconsistent with not using array access. HHVM follows the <=3DPHP5.5 =
behaviour of
not allowing array access on a constant.

However, there is the massive BC break if the handling inside a string =
changes
--=20
Simon Welsh



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