Removal of ${} string interpolation in PHP 9

Hi everyone

It was pointed out to me that unfortunately the "Deprecate ${} string
interpolation" RFC didn't specify how the feature would be removed
in PHP 9.

https://wiki.php.net/rfc/deprecate_dollar_brace_string_interpolation
https://github.com/php/php-src/issues/8501

There are two approaches:

• Completely remove the syntax and make "${}" result in the literal string "${}"
• Keep the syntax in the parser but throw an error

It's pretty clear to me that the latter is preferable for two reasons:

1. People upgrading directly from <=PHP 8.1 to PHP 9.0 or people who
   have not addressed the deprecations will still get an appropriate
   compile-time error message instead of their code suddenly behaving
   differently.
2. We can reuse the syntax at some point without causing another BC break.

The only advantage of the former approach I can think of is easier (or
rather no) escaping of ${} in strings but this could also be a
drawback considering that it would become unclear what the original
intent of the code was (literal output or string interpolation).

So unless there are concerns I will amend that in the RFC.

Regards,
Ilija

In my reading of the RFC, I assumed the first approach: completely
remove the syntax and make "${}" result in the literal string "${}".

IMO, this is not an insignificant change to the RFC. I'd like to hear
from those who voted on the RFC before you make this change.

Cheers,
Ben

So unless there are concerns I will amend that in the RFC.

Erroring it out makes sense to me.

As we don't include any target version specification in PHP files, the
safest bet it so prevent the silent change from potentially leaking
through the introduction of a parser error.

I can understand removing this feature since it is a bit confusing, but are
there any plans to replace it - say with the template literal syntax of
JavaScript? For those needing to refactor having something to switch to
would be preferable than having the feature dropped. Or does PHP have some
goofy use for backtick that would prevent this from happening?

On Mon, May 23, 2022 at 6:59 AM Robert Landers landers.robert@gmail.com
wrote:

So unless there are concerns I will amend that in the RFC.

Erroring it out makes sense to me.

As we don't include any target version specification in PHP files, the
safest bet it so prevent the silent change from potentially leaking
through the introduction of a parser error.

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Ilija,

It might be a good idea to do up another RFC to make it easy to vote.
I suspect it won't be unanimous.

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