Description:
------------
php seems to fail to check if there is already a setcookie for the session in the queue and puts the same thing in again

Reproduce code:
---------------
<?php
ob_start();

session_start();
$id = session_id();

$_SESSION['asdf'] = 123;

var_dump($_SESSION);
session_write_close();

$_SESSION['asdff'] = 234;

var_dump($_SESSION);
session_start($id);

$_SESSION['a'] = 'b';

var_dump($_SESSION);
session_write_close();

var_dump($_SESSION);


Expected result:
----------------
X-Powered-By: PHP/5.2.1-dev
Set-Cookie: PHPSESSID=h00e0fl7o9ilgifoluqh8kdbg1; path=/
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
Content-type: text/html

array(1) {
  ["asdf"]=>
  int(123)
}
array(2) {
  ["asdf"]=>
  int(123)
  ["asdff"]=>
  int(234)
}
array(2) {
  ["asdf"]=>
  int(123)
  ["a"]=>
  string(1) "b"
}
array(2) {
  ["asdf"]=>
  int(123)
  ["a"]=>
  string(1) "b"
}


Actual result:
--------------
X-Powered-By: PHP/5.2.1-dev
Set-Cookie: PHPSESSID=h00e0fl7o9ilgifoluqh8kdbg1; path=/
Set-Cookie: PHPSESSID=h00e0fl7o9ilgifoluqh8kdbg1; path=/
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0
Pragma: no-cache
Content-type: text/html

array(1) {
  ["asdf"]=>
  int(123)
}
array(2) {
  ["asdf"]=>
  int(123)
  ["asdff"]=>
  int(234)
}
array(2) {
  ["asdf"]=>
  int(123)
  ["a"]=>
  string(1) "b"
}
array(2) {
  ["asdf"]=>
  int(123)
  ["a"]=>
  string(1) "b"
}