Description:
------------
Not sure whether this is a bug or a feature, so reporting this for someone else to make that determination.

PCRE used to find a match using the below example code on PHP < 7.3, but no longer matches on PHP 7.3.

See: https://3v4l.org/lunKA

Is suspect the behavioural change is related to the implementation of PCRE 2 in PHP 7.3 - https://wiki.php.net/rfc/pcre2-migration .

Test script:
---------------
setlocale(LC_ALL, 'C');
var_dump(preg_match('`^\w+$`u', 'Iñtërnâtiônàlizætiøn'));

Expected result:
----------------
I'd expected the results of the regex to be the same cross-version.