Re: Interpolation using ${} syntax with spaces inside the braces

> On 15/04/2016, at 9:40 AM, Sara Golemon <pollita@php.net> wrote: > > 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. >> > Right. Which is why I'm conflicted on bug/not-bug/different-bug. > > 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. > > 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. > > So the question becomes: What's the right move going forward. My > inclination would be to either: > A: Ignore surrounding whitespace within the ${...} expression. > Essentially, adopt HHVM's output for these examples. > B: Throw an error on surrounding whitespace. This will make > discovering timebombs like these in existing code easier to catch. > > In either case, if the programmer actually did want the > constant->variable double-interpolation, that could be easily achieved > via "${(foo)}" which disambiguated foo as a variable name from foo as > an expression. > > -Sara > >> Is this related to the use of quotes around string array keys inside >> strings? >> >> e.g. "$foo[great]" does not evaluate to $foo['my'] but to >> $foo['great']. >> > 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. > > -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 “correct” 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 <=PHP5.5 behaviour of not allowing array access on a constant. However, there is the massive BC break if the handling inside a string changes -- Simon Welsh

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