Session doesnot work in nginx. php-fpm create new session file every time

My application cannot read (already created ) session file. so when I try to make two file 1.php:

session_start();
$_SESSION['test']="Digital_Ocean";

2.php:

session_start();
echo $_SESSION['test']

when I browser 1.php, it will crease a session file(in session.save_path) sess_… with out error. When browse 2.php again create another sess_… file with error: ** Notice: Undefined index:test** I have given access to the session folder

chmod -R 0777 /var/lib/php5/session

(same problem when I use /tmp also)

That’s the reason I cannot login in any php application. can anyone explain me what’s going on?

I have nginx, varnish and php-fpm Thank you