session_set_save_handler() sets
the user-level session storage functions which are used for
storing and retrieving data associated with a session. This
is most useful when a storage method other than those
supplied by PHP sessions is preferred. i.e. Storing the
session data in a local database. 成功回傳TRUE失敗回傳FALSE。
注: The "write" handler is not executed until after the output stream is closed. Thus, output from debugging statements in the "write" handler will never be seen in the browser. If debugging output is necessary, it is suggested that the debug output be written to a file instead.
注: The write handler is not executed if the session contains no data; this applies even if empty session variables are registered. This differs to the default file-based session save handler, which creates empty session files.
The following example provides file based session
storage similar to the PHP sessions default save handler files. This example could
easily be extended to cover database storage using your
favorite PHP supported database engine.
Read function must return string value always to make
save handler work as expected. Return empty string if there
is no data to read. Return values from other handlers are
converted to boolean expression. TRUE for success, FALSE for
failure.
See also the
session.save_handler configuration directive.