Description:
------------
If localhost/p1.php initiates a session before redirecting to 127.0.0.1/p2.php (or vice versa), the session data will be saved in p1 but not restored in p2; a new session will be started in p2.  

Only if the host references match literally ( both 'localhost' or both '127.0.0.1' ) will the session be restored.

Reproduce code:
---------------
Create 2 files, truncate sessions for a clean start ( I store sessions  in a mysql db, and 'incSessions.inc' are the vanilla routines that support that)

_t1.php:

<?php define('cDocRoot',$_SERVER['DOCUMENT_ROOT'].'/') ;
    require_once( cDocRoot.'Global/incSessions.inc' ) ;
    session_start() ;

    $_SESSION['T1'] = session_id() ;
    header('Location: http://127.0.0.1/_t2.php') ;
    exit() ;
?>    

_t2.php:

<?php define('cDocRoot',$_SERVER['DOCUMENT_ROOT'].'/') ;
    require_once( cDocRoot.'Global/incSessions.inc' ) ;
    session_start() ;

    $_SESSION['T2'] = session_id() ;
    var_dump($_SESSION) ;
    exit() ;
?>

Type into the address line of your browser "127.0.0.1/_t1.php", and note that var_dump shows both 'T1' and 'T2' having been set.  Inspect the sessions storage, note that only one session was created.

Re-truncate sessions, and call _t1 as "localhost/_t1.php".  Note that var_dump now shows only 'T2' having a value, and that inspection of the sessions storage shows 2 sessions rather than 1.

Expected result:
----------------
I expected the session to be restored after the redirect regardless of how localhost was identified.

Actual result:
--------------
See above