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Date: Thu, 23 Sep 2021 16:31:48 +1000
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Subject: [RFC] Locale-independent case conversion
From: tstarling@wikimedia.org (Tim Starling)

Please consider my RFC for locale-independent case conversion.

https://wiki.php.net/rfc/strtolower-ascii
https://github.com/php/php-src/pull/7506

The RFC and associated PR ended up going some way beyond the original
scope, because for consistency, it's best if everything has the same
concept of case folding. I saw this as an opportunity to clean up a
common kind of locale-dependence in PHP which was previously inconsistent.

So not only will strtolower() and strtoupper() become
locale-independent, converting only ASCII, but also stristr, stripos,
strripos, lcfirst, ucfirst, ucwords, str_ireplace, the array sorting
functions with SORT_FLAG_CASE, and array_change_key_case.

Also, I changed a number of internal functions to use ASCII case
folding, giving rise to a range of effects in callers throughout the
core tree. The effects are all documented in the RFC.

I am proposing that locale-sensitive case conversion be provided with
the new names ctype_tolower() and ctype_toupper(). Those names might
seem odd at first glance, but they are wrappers for functions in
ctype.h and work in a very similar way to the rest of the ctype extension.

-- Tim Starling