CREATE TABLE `session` (`skey` char(32) CHARACTER SET ascii NOT NULL,`data` text COLLATE utf8mb4_bin,`expire` int(11) NOT NULL,PRIMARY KEY (`skey`),KEY `index_session_expire` (`expire`) USING BTREE) ENGINE=MyISAM DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;

<?php/** 連接數據庫所需的DNS、用戶名、密碼等，一般情況不會在代碼中進行更改，* 所以使用常量的形式，可以避免在函數中引用而需要global。*/define('SESSION_DNS', 'mysql:host=localhost;dbname=db;charset=utf8mb4');define('SESSION_USR', 'usr');define('SESSION_PWD', 'pwd');define('SESSION_MAXLIFETIME', get_cfg_var('session.gc_maxlifetime'));//創建PDO連接//持久化連接可以提供更好的效率function getConnection() {try {$conn = new PDO(SESSION_DNS, SESSION_USR, SESSION_PWD, array(PDO::ATTR_PERSISTENT => TRUE,PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,PDO::ATTR_EMULATE_PREPARES => FALSE));return $conn;} catch (Exception $ex) {}}//自定義的session的open函數function sessionMysqlOpen($savePath, $sessionName) {return TRUE;}//自定義的session的close函數function sessionMysqlClose() {return TRUE;}/** 由于一般不會把用戶提交的數據直接保存到session，所以普通情況不存在注入問題。* 且處理session數據的SQL語句也不會多次使用。因此預處理功能的效益無法體現。* 所以，實際工程中可以不必教條的使用預處理功能。*//** sessionMysqlRead()函數中，首先通過SELECT count(*)來判斷sessionID是否存在。* 由于MySQL數據庫提供SELECT對PDOStatement::rowCount()的支持，* 因此，實際的工程中可以直接使用rowCount()進行判斷。*///自定義的session的read函數//SQL語句中增加了“expire > time()”判斷，用以避免讀取過期的session。function sessionMysqlRead($sessionId) {try {$dbh = getConnection();$time = time();$sql = 'SELECT count(*) AS `count` FROM session '. 'WHERE skey = ? and expire > ?';$stmt = $dbh->prepare($sql);$stmt->execute(array($sessionId, $time));$data = $stmt->fetch(PDO::FETCH_ASSOC)['count'];if ($data = 0) {return '';}$sql = 'SELECT `data` FROM `session` '. 'WHERE `skey` = ? and `expire` > ?';$stmt = $dbh->prepare($sql);$stmt->execute(array($sessionId, $time));$data = $stmt->fetch(PDO::FETCH_ASSOC)['data'];return $data;} catch (Exception $e) {return '';}}//自定義的session的write函數//expire字段存儲的數據為當前時間+session生命期，當這個值小于time()時表明session失效。function sessionMysqlWrite($sessionId, $data) {try {$dbh = getConnection();$expire = time() + SESSION_MAXLIFETIME;$sql = 'INSERT INTO `session` (`skey`, `data`, `expire`) '. 'values (?, ?, ?) '. 'ON DUPLICATE KEY UPDATE data = ?, expire = ?';$stmt = $dbh->prepare($sql);$stmt->execute(array($sessionId, $data, $expire, $data, $expire));} catch (Exception $e) {echo $e->getMessage();}}//自定義的session的destroy函數function sessionMysqlDestroy($sessionId) {try {$dbh = getConnection();$sql = 'DELETE FROM `session` where skey = ?';$stmt = $dbh->prepare($sql);$stmt->execute(array($sessionId));return TRUE;} catch (Exception $e) {return FALSE;}}//自定義的session的gc函數function sessionMysqlGc($lifetime) {try {$dbh = getConnection();$sql = 'DELETE FROM `session` WHERE expire < ?';$stmt = $dbh->prepare($sql);$stmt->execute(array(time()));$dbh = NULL;return TRUE;} catch (Exception $e) {return FALSE;}}//自定義的session的session id設置函數/** 由于在session_start()之前，SID和session_id()均無效，* 故使用$_GET[session_name()]和$_COOKIE[session_name()]進行檢測。* 如果此兩者均為空，則表明session尚未建立，需要為新session設置session id。* 通過MySQL數據庫獲取uuid作為session id可以更好的避免session id碰撞。*/function sessionMysqlId() {if (filter_input(INPUT_GET, session_name()) == '' andfilter_input(INPUT_COOKIE, session_name()) == '') {try {$dbh = getConnection();$stmt = $dbh->query('SELECT uuid() AS uuid');$data = $stmt->fetch(PDO::FETCH_ASSOC)['uuid'];$data = str_replace('-', '', $data);session_id($data);return TRUE;} catch (Exception $ex) {return FALSE;}}}//session啟動函數，包括了session_start()及其之前的所有步驟。function startSession() {session_set_save_handler('sessionMysqlOpen','sessionMysqlClose','sessionMysqlRead','sessionMysqlWrite','sessionMysqlDestroy','sessionMysqlGc');register_shutdown_function('session_write_close');sessionMysqlId();session_start();}