title: preg_match with international characters and accents
body: <p>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</p>
  
  <pre><code>$string = 'é';
  
  if(preg_match('/^[\p{L}]+$/i', $string)){
  
      echo 'ok';
  
  } else{
  
      echo 'nok';
  }
  </code></pre>