title: PHP preg_replace regexp for dash
body: <p>I am trying to replace anything in the string that is not a letter, number, or dash "-".</p>
  
  <p>How do I modify this line to include the dash?</p>
  
  <pre><code>$link = preg_replace('/[^a-z0-9]/', "", strtolower($_POST['link_name']));
  </code></pre>
  
  <p>Do I just insert it in there?</p>
  
  <pre><code>$link = preg_replace('/[^a-z0-9-]/', "", strtolower($_POST['link_name']));
  </code></pre>