====== PHP RFC: Multibyte for levenshtein, mb_levenshtein function ======
  * Version: 0.1
  * Date: 2024-09-25
  * Author: Yuya Hamada, youkidearitai@gmail.com
  * Status: Draft
  * First Published at: http://wiki.php.net/rfc/mb_levenshtein

===== Introduction =====
Multibyte levenshtein distances have feature requests in the past. Therefore, we would like to create the mb_levenshtein function to implement this.

ref: [[https://github.com/php/php-src/issues/10180]]

===== Proposal =====
Add mb_levenshtein function.

<code>
function mb_levenshtein(string $string1, string $string2, int $insertion_cost = 1, int $replacement_cost = 1, int $deletion_cost = 1, ?string $encoding = null): int {}
</code>

===== Backward Incompatible Changes =====
This could break a function existing in userland with the same name.


===== Proposed PHP Version(s) =====
PHP 8.5

===== RFC Impact =====
==== To SAPIs ====
To SAPIs Will add the aforementioned functions to all PHP environments.


==== To Existing Extensions ====
Adds mb_levenshtein() to the mbstring extension. 

==== To Opcache ====
No effect.

==== New Constants ====
No new constants.

==== php.ini Defaults ====
No changed php.ini settings.

===== Open Issues =====
https://github.com/php/php-src/issues/10180

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


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


===== Voting =====
TBD.

===== Implementation =====
https://github.com/php/php-src/pull/16043

===== References =====
Userland implementation is here:
  * https://github.com/KEINOS/mb_levenshtein
  * https://qiita.com/mpyw/items/2b636827730e06c71e3d#%E5%AE%9F%E8%A3%85 (Japanese page)


===== Rejected Features =====
Keep this updated with features that were discussed on the mail lists.