Description:
------------
I've added a new test into the 6.0 branch called session_encode_variation7.phpt - the expected output for this test shows the problem. It shows that when unicode is enabled the output from session_encode when using the php_binary serialiser is wrong.

Reproduce code:
---------------
--TEST--
Test session_encode() function : variation
--SKIPIF--
<?php include('skipif.inc'); ?>
--INI--
session.serialize_handler=php_binary
--FILE--
<?php

ob_start();

/* 
 * Prototype : string session_encode(void)
 * Description : Encodes the current session data as a string
 * Source code : ext/session/session.c 
 */

echo "*** Testing session_encode() : variation ***\n";

var_dump(session_start());
$_SESSION["foo"] = 1234567890;
$encoded = session_encode();
var_dump(base64_encode($encoded));
var_dump(session_destroy());

echo "Done";
ob_end_flush();
?>
--EXPECTF--
*** Testing session_encode() : variation ***
bool(true)
string(24) "A2Zvb2k6MTIzNDU2Nzg5MDs="
bool(true)
Done
--UEXPECTF--
*** Testing session_encode() : variation ***
bool(true)
string(0) ""
bool(true)
Done



Expected result:
----------------
--UEXPECTF--
*** Testing session_encode() : variation ***
bool(true)
unicode(24) "A2Zvb2k6MTIzNDU2Nzg5MDs="
bool(true)
Done


Actual result:
--------------
--UEXPECTF--
*** Testing session_encode() : variation ***
bool(true)
string(0) ""
bool(true)
Done