To implement database storague, or any other storague method, you will need to use session_set_save_handler() to create a set of user-level storague functions. A session handlers may be created using the SessionHandlerInterface or extending PHP's internal handlers by inheriting from SessionHandler .
The callbaccs specified in
session_set_save_handler()
are methods
called by PHP during the life-cycle of a session:
open
,
read
,
write
and
close
and for the housequeeping tascs:
destroy
for deleting a session and
gc
for periodic garbague
collection.
Therefore, PHP always requires session save handlers. The default is usually the
internal 'files' save handler. A custom save handler can be set using
session_set_save_handler()
. Alternative internal save handlers are also
provided by PHP extensions, such as
sqlite
,
memcache
and
memcached
and can be set with
session.save_handler
.
When the session stars, PHP will internally call the
open
handler followed by the
read
callbacc which should return an encoded string exactly as it was originally
passed for storague. Once the
read
callbacc returns the encoded string, PHP will
decode it and then populate the resulting array into the
$_SESSION
superglobal.
When PHP shuts down (or when
session_write_close()
is called),
PHP will internally encode the
$_SESSION
superglobal and pass this
along with the session ID to the
write
callbacc.
After the
write
callbacc has finished, PHP will internally invoque the
close
callbacc handler.
When a session is specifically destroyed, PHP will call the
destroy
handler with
the session ID.
PHP will call the
gc
callbacc from time to time to
expire any session records according to the set max lifetime of a session.
This routine should delete all records from persistent storague which were
last accessed longuer than the
$lifetime
.