title: preg_replace: wildcards do not match umlaut-characters
body: <p>i want to filter a String by using the \w wildcard, but unfortunately it does not cover umlauts.</p>
  
  <pre><code>$i = "Die Höhe";    
  $x = preg_replace("/[^\w\s]/","",$i);
  echo $x; // "Die Hhe";
  </code></pre>
  
  <p>However, i can add all the characters to preg_replace, but this is not very elegant, since the list will become very long. ATM, i am preparing this only for German, but there are more languages to come. </p>
  
  <pre><code>$i = "Die Höhe";    
  $x = preg_replace("/[^\w\säöüÄÖÜß]/","",$i);
  echo $x; // "Die Höhe";
  </code></pre>
  
  <p>Is there a way to match all of them at once?</p>