PHP RFC: Add locale for case insensitive grapheme functions

• Version: 0.9
• Date: 2025-06-07
• Author: Yuya Hamada, youkidearitai@gmail.com
• Status: Draft
• First Published at: https://wiki.php.net/rfc/grapheme_add_locale_for_case_insensitive

A grapheme functions is not locale dependency. This RFC is add locale parameter for grapheme case insensitive functions. That is more enhancements for Unicode can be expected.

• grapheme_stripos
• grapheme_strripos
• grapheme_stristr
• grapheme_levenshtein

By this RFC can cover locale. For example.

var_dump(grapheme_stripos("i", "\u{0130}", 0, "tr_TR")); // Result is 0
var_dump(grapheme_stripos("i", "\u{0130}", 0, "en_US")); // Result is false

Add a $locale parameter in these functions.

function grapheme_stripos(string $haystack, string $needle, int $offset = 0, ?string $locale = null): int|false
function grapheme_strripos(string $haystack, string $needle, int $offset = 0, ?string $locale = null): int|false
function grapheme_stristr(string $haystack, string $needle, bool $beforeNeedle = false, ?string $locale = null): string|false 
function grapheme_levenshtein(string $string1, string $string2, int $insertion_cost = 1, int $replacement_cost = 1, int $deletion_cost = 1, ?string $locale = null): int|false

Maybe nothing.

8.5

No effects.

No effects.

No effects.

No effects.

Nothing.

This section details areas where the feature might be improved in future, but that are not currently proposed in this RFC.

Include these so readers know where you are heading and can discuss the proposed voting options.

https://github.com/php/php-src/pull/18792

https://github.com/php/php-src/pull/18792

https://unicode-org.github.io/icu/userguide/transforms/casemappings.html#full-language-specific-case-mapping

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