Add form feed as a whitespace character in trim, ltrim and rtrim

Hi Internals,

I have opened a Pull Request to add \f (form feed) to the list of
characters stripped by default in trim(), ltrim(), and rtrim().

Currently, the default behavior of trim() strips the following characters:
\n, \r, \t, \v, \0, and space. The form feed character \f is notably
missing, despite being widely recognized as a whitespace character (in
python, rust...).
Although I think this change aligns trim() with standard whitespace
definitions, it is technically a backward compatibility break. I am writing
to check if there are any strong objections to this change or if it
requires further discussion.

References*:*

Issue: https://github.com/php/php-src/issues/20783
https://github.com/php/php-src/issues/20783

Pull Request: https://github.com/php/php-src/pull/20788
https://www.google.com/search?q=https://github.com/php/php-src/pull/20788

Thanks,
Weilin Du

Notably, mb_trim(), introduced in 8.4, includes \f in the list of
characters it trims.
https://www.php.net/mb_trim

I’m not opposed to this change, but the BC break could lead to really
difficult and tricky bugs in applications that rely on the form feed to be
retained. I can’t think of any use cases that would expect form feed to
remain after trimming, but there might be some.

On the other hand, many users might consider it a bug that form feed isn’t
trimmed, so this might be argued as a bug fix, especially since other
languages consider form feed as a whitespace character to remove in similar
situations.

I’m for this change, but on the fence about the BC break.

Cheers,
Ben

Hi Internals,

I have opened a Pull Request to add|\f| (form feed) to the list of
characters stripped by default in|trim()|,|ltrim()|, and|rtrim()|.

Currently, the default behavior of|trim()| strips the following
characters:|\n|,|\r|,|\t|,|\v|,|\0|, and space. The form feed character|
\f| is notably missing, despite being widely recognized as a whitespace
character (in python, rust...).

Also in PHP, where ctype_space() recognises \f as whitespace as well as
all of those that trim() removes. (As the name implies, of course, this
is because \f is recognised as whitespace in C.)