pdf表单发送FDF而不是PDF

UPDATE i discovered it sends PDF if opened by adobe reader at my computer, but same pdf form sends FDF if opened in Chrome browser at website UPDATE END

i am using Acrobat XI Pro trial version

Adobe Acrobat offer forms in pdf documents, those forms can be submitted to server

submit button settings http://gyazo.com/0ff0dc17210f39f062a131c85265406c

my server code

<?php

ob_start();
$file = file_get_contents("php://input"); //Gets binary PDF Data
$time = microtime(true);
$newfile = "./customers/" . $time . ".pdf"; //Names file based on the time to the microsecond so nothing gets overwritten.
$worked = file_put_contents($newfile, $file); //Creates File
ob_end_clean();

?>

and i am getting FDF data instead, not PDF document

In general Adobe PDF Forms full functionality available only in Adobe Reader. Google Chrome pdf viewer sends only FDF format. Firefox pdf viewer don't allow form editing/sending at all. Maybe obvious, but i am php developer and never worked with PDF Forms.