Php :: SimpleXML, CDATA And HTML Entities - Tags Are Interpreted With Their HTML Entity Equivalents?

trying to work with "simple" XML for the first time. I'm building a small CMS for a Flash based site and the content is held in an XML file. My problem is that many of the copy fields are XML CDATA fields. on the one hand, with:

$xml = simplexml_load_file($file, 'SimpleXMLElement', LIBXML_NOCDATA);

I can pull the data out of that node and the CDATA tags are stripped. My issues come with trying to save the data with:

file_put_contents($file, $xml->asXML());

Problems are: a) tags are interpreted with their HTML entity equivalents. I don't want this to happen.I gather this is coming from the asXML method because even if I do anhtml_entity _decode on the $_POST data it's still being converted.

b) because of the above, there's no way to add the CDATA tags because they also have their charachters converted.