preg_match with international characters and accents

I would like to validate a string with a pattern that can only contain letters (including letters with accents). Here is the code I use and it always returns “nok”. I don’t know what I am doing wrong, can you help? thanks

$string = 'é';

if(preg_match('/^[p{L}]+$/i', $string)){

    echo 'ok';

} else{

    echo 'nok';
}

Answer

Add the UTF-8 modifier flag (u) to your expression:

/^p{L}+$/ui

There is also no need to wrap p{L} inside of a character class.