title: PHP preg_replace for hex
body: <p>I'm trying to use <code>preg_replace()</code> to remove all hexadecimal characters in a string (with only lower case letters):</p>
  
  <pre><code>$line = "sjdivfriyaaqa\xd2vkmpcuyyuen";
  $line = preg_replace('/\\x[0-9a-f]{2}/', '', $line);
  echo($line);
  </code></pre>
  
  <p>This should, as I understand it, echo <code>sjdivfriyaaqavkmpcuyyuen</code> (<code>$line</code> with <code>\xd2</code> removed) but it echoes the original <code>$line</code>. Why?</p>