FDF quit work for Acrobat 6

Launching a PDF form from PHP is easy (got the code below from php.net).
Anyway this method works with Acrobat 5 readers and not Acrobat 6. Does
anyone know why?
thanks,
-eric wood

<<<<<<<<<snip>>>>>>>>
$fdfdata = "%FDF-1.2\n%~B~D~\~T\n";
$fdfdata .= "1 0 obj \n<< /FDF ";
$fdfdata .= "<< /Fields [\n";
foreach($values as $key=>$val)
{
$fdfdata.="<< /V ($val)/T ($key) >> ";
}
$fdfdata .= "]\n";
$fdfdata .= "/F (http://www.pdfs.com/Invoice.pdf)>>";
$fdfdata .= ">>\nendobj\ntrailer\n<<\n/Root 1 0 R\n>>\n";
$fdfdata .= "%%EOF";

header ("Content-Type: application/vnd.fdf");
print $fdfdata;
<<<<<<<<<snap>>>>>>>>