sendAndLoad problem

this is a simple test code to send and load xml data from a flash movie:
[AS]tgXML = new XML("<data><m nick=“Adela” colour=“000000”>Nuevo%20tagboard%2C%20pueden%20escribir%20lo%20que%20quieran%20sobre%20la%20p%C3%A1gina%20aqu%C3%AD%2E</m><m nick=“io” colour=“ff0000”>Nuevo%20mensaje%20escrito%20por%20mi</m></data>");
tgXML.ignoreWhite = true;
tgRecipiente = new XML();
tgRecipiente.ignoreWhite = true;
tgRecipiente.onLoad = function(){
campo.text = tgRecipiente.firstChild;}
its very similar to the one of the xml guestbook in this site, and because I copied the whole php script from there, there’s nothing wrong with it.
the problem is that this script isn’t sending anything and everytime i run it it ereases the xml file. WHY???

which php script is that?

$xmlString = $HTTP_RAW_POST_DATA;
if($xmlString != NULL){
$file = fopen("tagboard.xml", "w+") or die("Can't open XML file");
if(!fwrite($file, $xmlString)){
	print "Error writing to XML-file";
print $xmlString."
else {print "no data was sent";}

try replacing $HTTP_RAW_POST_DATA; with readfile(“php://input”); and see if that helps

ooooooo you’re a genius!!! it worked
but why?
the other code used to work with the guestbook