title: Matching UTF Characters with preg_match in PHP: (*UTF8) Works on Windows but not Linux
body: <p>I have a simple regular expression to check a username:</p>
  
  <pre><code>preg_match('/(*UTF8)^[[:alnum:]]([[:alnum:]]|[ _.-])+$/i', $username);
  </code></pre>
  
  <p>In local testing (Windows 7 using WAMP), this will allow for usernames using UTF characters (such as é or ñ). However, when I move to test this on the server where the site will actually be hosted, I get the following warning:</p>
  
  <blockquote>
    <p>Warning: preg_match() [function.preg-match]: Compilation failed: (*VERB) not recognized at offset 5 in /home/sites/vgmusic.com/test/Core/Impl/FormElementValidator.php on line 12</p>
  </blockquote>
  
  <p>I have also tried this on a local Ubuntu installation and get the same error. In fact, I've only seen this work on my local development environment. Is there a way to allow for special characters that will work for all operating systems?</p>