<?php/* 使用数据库保存session */class DBHandler implements SessionHandlerInterface {protected $dbh;public function open($save_path, $name) {try {$this->connect($save_path, $name);return true;} catch(PDOException $e) {echo $e->getMessage();return false;}}public function close() {return true;}public function destroy($session_id) {$sth = $this->dbh->prepare("DELETE FROM sessions WHERE session_id = ?");$sth->execute(array($session_id));return true;}public function gc($maxlifetime) {$sth = $this->dbh->prepare("DELETE FROM sessions WHERE last_update < ?");$sth->execute(array(time() - $maxlifetime));return true;}public function read($session_id) {$sth = $this->dbh->prepare("SELECT session_data FROM sessions WHERE session_id = ?");$sth->execute(array($session_id));$row = $sth->fetch(PDO::FETCH_NUM);if(count($row) == 0) {return '';} else {return $row[0];}}public function write($session_id, $session_data) {date_default_timezone_set('PRC');$now = time();$sth = $this->dbh->prepare("UPDATE sessions SET session_data = ?,last_update = ? WHERE session_id = ?");$sth->execute(array($session_data, $now, $session_id));if($sth->rowCount() == 0) {$sth2 = $this->dbh->prepare("INSERT INTO sessions (session_id, session_data, last_update) VALUES (?,?,?)");$sth2->execute(array($session_id, $session_data, $now));}}public function createTable($save_path, $name, $connect = true) {if($connect) {$this->connect($save_path, $name);}$sql =<<<_SQL_
CREATE TABLE sessions (session_id VARCHAR(64) NOT NULL,session_data MEDIUMTEXT NOT NULL,last_update INT NOT NULL,PRIMARY KEY (session_id)
)
_SQL_;$this->dbh->exec($sql);}public function connect($save_path) {$parts = parse_url($save_path);parse_str($parts['query'], $query);//$dsn格式：mysql:host=localhost;dbname=test$dsn = $parts['scheme'].":host=".$parts['host'].";dbname=".$query['dbname'];$user = $query['user'];$password = $query['password'];$this->dbh = new PDO($dsn, $user, $password);$this->dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);try {$this->dbh->query('SELECT 1 FROM sessions LIMIT 1');} catch(Exception $e) {$this->createTable($save_path, NULL, false);}}
}

<?phpinclude './db.php';ini_set('session.save_path', "mysql://localhost?user=root&password=&dbname=test");
ini_set('session.gc_maxlifetime', 5);
ini_set('session.gc_divisor', 2);
session_set_save_handler(new DBHandler);session_start();if(! isset($_SESSION['visits'])) {$_SESSION['visits'] = 0;
}$_SESSION['visits']++;
echo '你是第 '.$_SESSION['visits'].' 次访问';