Argument passed to save_handler. In the case of files, this is the path
where data files are stored. Note: Windows users have to change this
variable in order to use PHP's session functions.

As of PHP 4.0.1, you can define the path as:

   session.save_path = "N;/path"

where N is an integer. Instead of storing all the session files inv
/path, what this will do is use subdirectories N-levels deep, and
store the session data in those directories. This is useful if you
or your OS have problems with lots of files in one directory, and is
a more efficient layout for servers that handle lots of sessions.

NOTE 1: PHP will not create this directory structure automatically.

       You can use the script in the ext/session dir for that purpose.

NOTE 2: See the section on garbage collection below if you choose to

       use subdirectories for session storage

The file storage module creates files using mode 600 by default.
You can change that by using

   session.save_path = "N;MODE;/path"

where MODE is the octal representation of the mode. Note that this
does not overwrite the process's umask.

ini_set(„session.save_path“, $BS_DIR.„/tmp“);
php.ini:
session.save_path = „/tmp“