How do I match accented characters with PHP preg?

Question

I’d like to give my users the option to not only fill in letters and numbers, but also “special” letters like the “á”, “é”, etc. However, I do not want them to be able to us

Answer 1

What characters are considered "word-characters" depends on the locale. You should set a locale which has those characters in its natural alphabet, and use the /u modifier for the regexp, like this:

$str = 'perché';
setlocale(LC_ALL, 'it_IT@euro');
echo preg_match('#^\w+$#u', $str);