[PHP-DEV] Add form feed as a whitespace character in trim, ltrim and rtrim

Mailing Lists php.internals
1

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**:**

Thanks,
Weilin Du

2

On Sat, Dec 27, 2025 at 04:40 LamentXU <lamentxu@163.com> wrote:

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**:**

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

3

On 2025-12-27 23:38, LamentXU wrote:

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.)

4

On 2025-12-28 11:53, Morgan wrote:

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.)

Uh, except of course for NUL, which trim() removes.