How redirect $_FILES Array?

I have three php file. There is form with text fields and file upload in the A.php I post A.php to B.php. In the B.php there is confirmation of text whit user typed in A.php. And there are input[type=hidden] fields with value of POST(which a posted from A.php) After confirmation in B.php I post to C.php. In c.php there is mail() function which send form fields to my mail. And i cant post file uploads (or $_FILES array) from B.php to C.php. How can i do it?

Source: stackoverflow-php