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Date: Thu, 11 Feb 2016 12:46:20 +0000
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Subject: Re: [PHP-DEV] [RFC] Generalize support of negative string offsets
From: rowan.collins@gmail.com (Rowan Collins)

Christoph Becker wrote on 11/02/2016 12:16:
> Appending to an array always adds a single element only, consider
>
>    $a = [1,2,3];
>    $a[] = [4,5];
>
> The suggested syntax for strings would concatenate an arbitrary amount
> of elements (characters) to a string.  IMHO, this would not be
> consistent, but rather confusing.  The alternative interpretation to
> append the first character only, would be confusing as well (besides
> there would be issues with regard to multibyte character encodings).

Indeed, this is a big problem with making the string offset 
functionality richer in general, because PHP has no "char" type, only a 
single-character string. This leads to some odd things:

// string[0] returns a one-char string, which has an element [0], so you 
can keep adding [0] for as long as you like:
$foo = 'abc';
echo $foo[0][0][0][0][0]; // a

// assignment to an offset only overwrites one character, but the source 
can be a string of any length:
$foo = 'abc';
$foo[0] = 'zzz';
echo $foo; // zbc

String offsets simply can't behave like array offsets within PHP's 
current type system, which is why I favour dedicating {} syntax to them, 
and making it work *usefully*, rather than trying to make it look like 
arrays. Then, it would be less surprising for $string{-1} to behave 
differently from $array[-1], and that $string{} is a syntax error.

Regards,
-- 
Rowan Collins
[IMSoP]