SimpleXMLElement support utf8

$utf8 = utf8_encode('2\x0F -8- 15');
$xml_user_info = new SimpleXMLElement("<?xml version=\"1.0\"?><user_info><a>2 -8- 15</a> <b>$utf8</b></user_info>");

$xml_file = $xml_user_info->asXML();

echo $xml_file;