title: PHP Regular expression - Remove all non-alphanumeric characters
body: <p>I use PHP.</p>
  
  <p><strong>My string can look like this</strong></p>
  
  <p><code>This is a string-test width åäö and some über+strange characters: _like this?</code></p>
  
  <p><strong>Question</strong></p>
  
  <p>Is there a way to remove non-alphanumeric characters and replace them with a space? Here are some non-alphanumeric characters:</p>
  
  <ul>
  <li>-</li>
  <li>+</li>
  <li>:</li>
  <li>_</li>
  <li>?</li>
  </ul>
  
  <p>I've read many threads about it but they don't support other languages, like this one:</p>
  
  <pre><code>preg_replace("/[^A-Za-z0-9 ]/", '', $string);
  </code></pre>
  
  <p><strong>Requirements</strong></p>
  
  <ul>
  <li>My list of none letter characters might not be complete.</li>
  <li>My content contain characters in different languages, like åäöü. Could be very many more.</li>
  <li>The non-alphanumeric characters should be replaced with a space. Else the word would be glued to eachother.</li>
  </ul>