using $output and $_POST

Hi,

thanks for your plugin it was really what I was looking for. By the way I’m creating a form which saves an xml files while pressing submit button.
I’m printing all the shortcodes of cf7 with $output .= $_POST[‘shortcode’]; but I’m not able to print any field of yours plugin. Any suggestions?
That’s a part of my code:

add_action( 'wpcf7_before_send_mail', 'CF7_pre_send' );
 
function CF7_pre_send($cf7) {
    $output = "";
    $output .= "<?xml version=\"1.0\" encoding=\"UTF-8\" ?><curriculum><cf>" . $_POST['codicefiscale'] . "</cf>";
    $output .= "<cognome>" . $_POST['cognome'] . "</cognome>";
	
 file_put_contents("wp-content/uploads/cf7outputtest.xml", $output);
}

Thanks a lot,

Luca