SESSION存放在数据库用法实例

<?php
/*
create table `ws_sessions` (
 `session_id` varchar(255) binary not null default '',
 `session_expires` int(10) unsigned not null default '0',
 `session_data` text,
 primary key (`session_id`)
) type=innodb;
*/
class session {
 // session-lifetime
 var $lifetime;
 // mysql-handle
 var $dbhandle;
 function open($savepath, $sessname) {
 // get session-lifetime
 $this->lifetime = get_cfg_var("session.gc_maxlifetime");
 // open database-connection
 $dbhandle = @mysql_connect("localhost","root","");
 $dbsel = @mysql_select_db("test",$dbhandle);
 // return success
 if(!$dbhandle || !$dbsel)
  return false;
 $this->dbhandle = $dbhandle;
 return true;
 }
 function close() {
 $this->gc(ini_get('session.gc_maxlifetime'));
 // close database-connection
 return @mysql_close($this->dbhandle);
 }
 function read($sessid) {
 // fetch session-data
 $res = mysql_query("select session_data as d from ws_sessions
    where session_id = '$sessid'
    and session_expires > ".time(),$this->dbhandle);
 // return data or an empty string at failure
 if($row = mysql_fetch_assoc($res))
  return $row['d'];
 return "";
 }
 function write($sessid,$sessdata) {
 // new session-expire-time
 $newexp = time() + $this->lifetime;
 // is a session with this id in the database?
 $res = mysql_query("select * from ws_sessions
    where session_id = '$sessid'",$this->dbhandle);
 // if yes,
 if(mysql_num_rows($res)) {
  // ...update session-data
  mysql_query("update ws_sessions
    set session_expires = '$newexp',
    session_data = '$sessdata'
    where session_id = '$sessid'",$this->dbhandle);
  // if something happened, return true
  if(mysql_affected_rows($this->dbhandle))
  return true;
 }
 // if no session-data was found,
 else {
  // create a new row
  mysql_query("insert into ws_sessions (
    session_id,
    session_expires,
    session_data)
    values(
    '$sessid',
    '$newexp',
    '$sessdata')",$this->dbhandle);
  // if row was created, return true
  if(mysql_affected_rows($this->dbhandle))
  return true;
 }
 // an unknown error occured
 return false;
 }
 function destroy($sessid) {
 // delete session-data
 mysql_query("delete from ws_sessions where session_id = '$sessid'",$this->dbhandle);
 // if session was deleted, return true,
 if(mysql_affected_rows($this->dbhandle))
  return true;
 // ...else return false
 return false;
 }
 function gc($sessmaxlifetime) {
 // delete old sessions
 mysql_query("delete from ws_sessions where session_expires < ".time(),$this->dbhandle);
 // return affected rows
 return mysql_affected_rows($this->dbhandle);
 }
}
$session = new session();
session_set_save_handler(array(&$session,"open"),
    array(&$session,"close"),
    array(&$session,"read"),
    array(&$session,"write"),
    array(&$session,"destroy"),
    array(&$session,"gc"));
session_start();
// etc...
?>