Installation

Session support is enabled in PHP by default. If
you would not like to build your PHP with session support, you
should specify the –disable-session option to configure.
To use shared memory allocation (mm) for session storage configure
PHP –with-mm[=DIR] .

The Windows version of PHP has built-in support
for this extension. You do not need to load any additional
extensions in order to use these functions.

Note:

By default, all data related to a particular
session will be stored in a file in the directory specified by the
session.save_path INI option. A file for each session (regardless
of if any data is associated with that session) will be created.
This is due to the fact that a session is opened (a file is
created) but no data is even written to that file. Note that this
behavior is a side-effect of the limitations of working with the
file system and it is possible that a custom session handler (such
as one which uses a database) does not keep track of sessions which
store no data.