Session保存到数据库的php类分享

<?php
class sessiontodb
{
private $_path = null;
private $_name = null;
private $_pdo = null;
private $_ip = null;
private $_maxlifetime = 0;

public function __construct(pdo $pdo)
{
session_set_save_handler(
array(&$this, 'open'),
array(&$this, 'close'),
array(&$this, 'read'),
array(&$this, 'write'),
array(&$this, 'destroy'),
array(&$this, 'gc')
);

$this->_pdo = $pdo;
$this->_ip = !empty($_server['remote_addr']) ? $_server['remote_addr'] : null;
$this->_maxlifetime = ini_get('session.gc_maxlifetime');
}

public function open($path,$name)
{
return true;
}

public function close()
{
return true;
}

public function read($id)
{
$sql = 'select * from session where phpsessid = ?';
$stmt = $this->_pdo->prepare($sql);
$stmt->execute(array($id));

if (!$result = $stmt->fetch(pdo::fetch_assoc)) {
return null;
} elseif ($this->_ip != $result['client_ip']) {
return null;
} elseif ($result['update_time']+$this->_maxlifetime < time()){
$this->destroy($id);
return null;
} else {
return $result['data'];
}
}

public function write($id,$data)
{
$sql = 'select * from session where phpsessid = ?';
$stmt = $this->_pdo->prepare($sql);
$stmt->execute(array($id));

if ($result = $stmt->fetch(pdo::fetch_assoc)) {
if ($result['data'] != $data) {
$sql = 'update session set update_time =? , date = ? where phpsessid = ?';

$stmt = $this->_pdo->prepare($sql);
$stmt->execute(array(time(), $data, $id));
}
} else {
if (!empty($data)) {
$sql = 'insert into session (phpsessid, update_time, client_ip, data) values (?,?,?,?)';
$stmt = $this->_pdo->prepare($sql);
$stmt->execute(array($id, time(), $this->_ip, $data));
}
}

return true;
}

public function destroy($id)
{
$sql = 'delete from session where phpsessid = ?';
$stmt = $this->_pdo->prepare($sql);
$stmt->execute(array($id));

return true;
}

public function gc($maxlifetime)
{
$sql = 'delete from session where update_time < ?';
$stmt = $this->_pdo->prepare($sql);
$stmt->execute(array(time() - $maxlifetime));

return true;
}
}

try{
$pdo = new pdo('mysql:host=localhost;dbname=rphp4zf', 'root','rickyfeng');
$pdo->setattribute(pdo::attr_errmode, pdo::errmode_exception);

new sessiontodb($pdo);
} catch(pdoexception $e) {
echo 'error: '.$e->getmessage();
}