Uncaught Error: Call to undefined function mb_regex_encoding() in .../vendor/voku/portable-utf8/src/voku/helper/UTF8.php:536

[MocioF]

I'm experiencing a PHP Fatal error while using portable-utf8 in a wordpress plugin when PHP is built with'--enable-mbstring' '--disable-mbregex' (which is the case, at the current date, for deployed WordPress/wordpress-playground).

As in topic, the error is:
Uncaught Error: Call to undefined function mb_regex_encoding() in .../vendor/voku/portable-utf8/src/voku/helper/UTF8.php:536

It seems that while detecting for UTF8 support,

portable-utf8/src/voku/helper/UTF8.php

Line 531 in a1333ac

self::$SUPPORT['mbstring'] = self::mbstring_loaded();

portable-utf8 checks for extension_loaded('mbstring')

portable-utf8/src/voku/helper/UTF8.php

Line 4535 in a1333ac

return \extension_loaded('mbstring');

and then it takes it for granted that mb_regex_encoding() is available.

portable-utf8/src/voku/helper/UTF8.php

Line 536 in a1333ac

\mb_regex_encoding('UTF-8');

But mb_regex_encoding() is available only when PHP is built without '--disable-regex' https://www.php.net/manual/en/mbstring.installation.php

A related possible problem is that symfony/polyfill-mbstring does not provide polyfills for mbregex function.
The only package I have found that can provide polyfill for mbregex is zendtech/polyfill-mb-ereg but even if it declares to provide a polyfill for mb_regex_encoding(), the code is:
https://github.com/zendtech/polyfill-mb-ereg/blob/813e5b2d0669a8c619e6b5439916b2e5d20d7af0/src/MbEreg.php#L58C1-L65C6
However I didn't test any patch to see what happens using this library.