XML encoding in PHP

I’ve needed it in JavaScript in the past and now I need it in PHP. Escape all those pesky special XML characters like so

  function XmlEncode($content)
  {
    $trans = array("&" => "&amp;", "<" => "&lt;", ">" => "&gt;", "'" => "&apos;",
      "\"" => "&quot;", "’" => "&apos;");
  	return strtr($content, $trans);
  }