The reason it does not qork is its embedded in html, calling a swf will work though.
Embed the recieving swf in some javascript embed code and it will work with the html too ( the textfield has to be in the main timeline ).
PHP Code:
<script language="JavaScript">
document.write ('<OBJECT classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000" '
+'codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=5,0,0,0" '
+'WIDTH=750 HEIGHT=500> <PARAM NAME=movie VALUE="knock.swf'+document.location.search+'">'
+'<PARAM NAME=quality VALUE=high>'
+'<EMBED src="knock.swf' +document.location.search+'" '
+'quality=high WIDTH=750 HEIGHT=500 '
+'TYPE="application/x-shockwave-flash"></EMBED></OBJECT>')
</script>