Your AS code seems to be right. So the problem might be in PHP. Please test first with this PHP file:
<?php
echo "test=1&done=true";
?>
This should then let your movie trace "true"
.
You then should debug your PHP. print_r($_POST);
destroys your output of course. May be you did forget to remove this debugging statement 🙂
@Jesse and @Ascension Systems, check the docs for URLVariables: http://livedocs.adobe.com/flash/9.0_de/ActionScriptLangRefV3/flash/net/URLVariables.html