如何使用数据库的方法来保存session

CREATE TABLE sessions (
sesskey char(32) not null,
expiry int(11) unsigned not null,
value text not null,
PRIMARY KEY (sesskey)
);

$SESS_DBHOST = "yourhost"; /* database server hostname */
$SESS_DBNAME = "yourdb"; /* database name */
$SESS_DBUSER = "youruser"; /* database user */
$SESS_DBPASS = "yourpassword"; /* database password */
$SESS_DBH = "";
$SESS_LIFE = get_cfg_var("session.gc_maxlifetime");

function sess_open($save_path, $session_name) {
global $SESS_DBHOST, $SESS_DBNAME, $SESS_DBUSER, $SESS_DBPASS, $SESS_DBH;

if (! $SESS_DBH = mysql_pconnect($SESS_DBHOST, $SESS_DBUSER, $SESS_DBPASS)) {echo "
Can't connect to $SESS_DBHOST as $SESS_DBUSER";echo "
MySQL Error: " . mysql_error();die;}

if (! mysql_select_db($SESS_DBNAME, $SESS_DBH)) {echo "
Unable to select database $SESS_DBNAME";die;}return true;}

function sess_close() {
return true;
}
function sess_read($key) {
global $SESS_DBH, $SESS_LIFE;
$qry = "SELECT value FROM session_tbl WHERE sesskey = '$key' AND expiry > " . time();
$qid = mysql_query($qry, $SESS_DBH);

if (list($value) = mysql_fetch_row($qid)) {
return $value;
}
return false;
}

function sess_write($key, $val) {
global $SESS_DBH, $SESS_LIFE;
$expiry = time() + $SESS_LIFE; //过期时间
$value = addslashes($val);
$qry = "INSERT INTO session_tbl VALUES ('$key', $expiry, '$value')";
$qid = mysql_query($qry, $SESS_DBH);

if (! $qid) {
$qry = "UPDATE session_tbl SET expiry = $expiry, value = '$value' WHERE sesskey = '$key' AND expiry > " . time();
$qid = mysql_query($qry, $SESS_DBH);
}
return $qid;
}
function sess_destroy($key) {
global $SESS_DBH;
$qry = "DELETE FROM session_tbl WHERE sesskey = '$key'";
$qid = mysql_query($qry, $SESS_DBH);
return $qid;
}

function sess_gc($maxlifetime) {
global $SESS_DBH;
$qry = "DELETE FROM session_tbl WHERE expiry < " . time();
$qid = mysql_query($qry, $SESS_DBH);
return mysql_affected_rows($SESS_DBH);
}

session_set_save_handler(
"sess_open",
"sess_close",
"sess_read",
"sess_write",
"sess_destroy",
"sess_gc");

session_start();
?>