PHP實戰
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實戰
<?php
/*
* 連接數據庫所需的DNS、用戶名、暗碼等,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()) == '' and
filter_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();
}