session_set_save_handler

    (PHP 4, PHP 5, PHP 7, PHP 8)

    session_set_save_handler — Устанавливает пользовательские обработчики хранения сессии

    Описание

    session_set_save_handler(
        callable $open,
        callable $close,
        callable $read,
        callable $write,
        callable $destroy,
        callable $gc,
        callable $create_sid = ?,
        callable $validate_sid = ?,
        callable $update_timestamp = ?
    ): bool

    Также возможно зарегистрировать следующий прототип:

    session_set_save_handler(object $sessionhandler, bool $register_shutdown = true): bool

    session_set_save_handler() устанавливает пользовательские обработчики хранения сессии, которые используются для сохранения и получения данных, связанных с сессией. Это особенно полезно, когда предпочтительным является метод хранения, отличный от тех, которые предоставляются сессиями PHP, например, хранение данных сессии в локальной базе данных.

    Список параметров

    Данная функция имеет два определения (прототипа).

    sessionhandler

    Экземпляр класса, реализующий интерфейс SessionHandlerInterface и необязательные SessionIdInterface и/или SessionUpdateTimestampHandlerInterface, такой как SessionHandler, для регистрации в качестве обработчика сессии.

    register_shutdown

    Зарегистрировать session_write_close() как функцию register_shutdown_function().

    или
    open

    Callback-функция со следующей сигнатурой:

    open(string $savePath, string $sessionName): bool

    Callback-функция open работает как конструктор в классах и выполняется при открытии сессии. Это первая callback-функция, которая выполняется, когда сессия стартует автоматически либо вручную через session_start(). Возвращаемое значение true в случае успешного выполнения, false в случае неудачи.

    close

    Callback-функция со следующей сигнатурой:

    close(): bool

    Callback-функция close работает как деструктор в классах и выполняется после того, как была вызвана callback-функция write. Она также вызывается при вызове session_write_close(). Возвращаемое значение должно быть true в случае успешного выполнения, false в случае неудачи.

    read

    Callback-функция со следующей сигнатурой:

    read(string $sessionId): string

    Callback-функция read должна всегда возвращать кодированную (сериализованную) строку сессии или пустую строку, если нет данных для чтения.

    Эта callback-функция вызывается внутренним механизмом PHP при старте сессии или при вызове session_start(). Перед тем, как будет вызвана эта callback-функция, PHP вызовет callback-функцию open.

    Возвращаемое значение данной callback-функции должно быть в точно таком же сериализованном формате, который изначально передавался для хранения в callback-функцию write. Возвращаемое значение будет автоматически десериализовано PHP и использовано для заполнения суперглобальной переменной $_SESSION. Даже если данные похожи на результат serialize(), стоит помнить, что это другой формат сериализации, который определён ini-директивой session.serialize_handler.

    write

    Callback-функция со следующей сигнатурой:

    write(string $sessionId, string $data): bool

    Callback-функция write вызывается, когда сессия должна быть сохранена и закрыта. Данная callback-функция принимает идентификатор текущей сессии и сериализованную версию суперглобальной переменной $_SESSION. Используемый внутри PHP метод сериализации определён ini-директивой session.serialize_handler.

    Переданные в эту callback-функцию сериализованные данные сессии должны быть сохранены в связи с переданным идентификатором сессии. При получении этих данных, callback-функция read должна вернуть то же самое значение, что было передано в callback-функцию write.

    Данная callback-функция вызывается, когда PHP завершает работу или явно при вызове session_write_close(). Следует помнить, что после выполнения этой callback-функции, PHP выполнит callback-функцию close.

    Замечание:

    Обработчик "write" не выполнится до тех пор, пока выходной поток не будет закрыт. Таким образом, вывод отладочных операторов в обработчике "write" никогда не отобразится в браузере. Если необходим вывод отладочной информации, рекомендуется записывать отладочные данные в файл.

    destroy

    Callback-функция со следующей сигнатурой:

    destroy(string $sessionId): bool

    Данная callback-функция вызывается, когда сессия уничтожается с помощью session_destroy() или при вызове session_regenerate_id() с параметром destroy, установленным в true. Возвращаемое значение должно быть true в случае успешного выполнения, false в случае неудачи.

    gc

    Callback-функция со следующей сигнатурой:

    gc(int $lifetime): bool

    Callback-функция сборщика мусора периодически вызывается PHP для очистки данных старых сессий. Частота контролируется директивами session.gc_probability и session.gc_divisor. Значение lifetime, которое передаётся в данную callback-функцию может быть установлено в session.gc_maxlifetime. Возвращаемое значение должно быть true в случае успешного выполнения, false в случае неудачи.

    create_sid

    Callback-функция со следующей сигнатурой:

    create_sid(): string

    Данная callback-функция выполняется, когда требуется новый идентификатор сессии. Не предусматривает параметров, а возвращаемое значение должно быть строкой, которая является допустимым идентификатором сессии для вашего обработчика.

    validate_sid

    Callback-функция со следующей сигнатурой:

    validate_sid(string $key): bool

    Callback-функция выполняется, когда должна быть запущена сессия, предоставляется идентификатор сессии и включается session.use_strict_mode. key - это идентификатор сессии для проверки. Идентификатор сессии действителен, если сессия с таким идентификатором уже существует. Возвращаемое значение должно быть true в случае успешного выполнения или false в случае возникновения ошибки.

    update_timestamp

    Callback-функция со следующей сигнатурой:

    update_timestamp(string $key, string $val): bool

    Callback-функция выполняется при сессии. key - это идентификатор сессии, val - это данные сессии. Возвращаемое значение должно быть true в случае успешного выполнения или false в случае возникновения ошибки.

    Возвращаемые значения

    Функция возвращает true в случае успешного выполнения или false, если возникла ошибка.

    Примеры

    Пример #1 Пользовательский обработчик сессии: полный код смотрите в описании SessionHandlerInterface.

    Здесь только продемонстрирован вызов session_set_save_handler, полный пример можно посмотреть в описании SessionHandlerInterface.

    Заметьте, что с session_set_save_handler() мы используем ООП-прототип и регистрируем функцию завершения, используя флаг параметра функции. Это обычно рекомендуется при регистрации объектов в качестве обработчиков хранения сессии.

    <?php
    class MySessionHandler implements SessionHandlerInterface
    {
    // здесь реализация интерфейса
    }

    $handler = new MySessionHandler();
    session_set_save_handler($handler, true);
    session_start();

    // устанавливаем и получаем значения по ключу из $_SESSION

    Примечания

    Внимание

    Обработчики write и close вызываются после деструктора объекта и поэтому не могут использовать его контекст или бросать исключения. Исключения не могут быть обработаны, так как не будут пойманы, не будет отражена трассировка стека исключения и выполнение просто прекратится неожиданно. Однако при этом, деструкторы объекта могут использовать сессии.

    Можно вызвать session_write_close() из деструктора, чтобы решить эту проблему "курицы и яйца", но самый надёжный способ - это регистрировать функцию завершения, как описано выше.

    Внимание

    Текущий рабочий каталог изменяется некоторыми SAPI, если сессия закрывается при завершении скрипта. Завершить сессию можно раньше с помощью session_write_close().

    Смотрите также

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    Инструкция • Исправление • Сообщение об ошибке
    ＋Добавить

    Примечания пользователей 41 notes

    up
    48
    andreipa at gmail dot com
    9 years ago
    After spend so many time to understand how PHP session works with database and unsuccessful attempts to get it right, I decided to rewrite the version from our friend stalker.

    //Database
    CREATE TABLE `Session` (
    `Session_Id` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
    `Session_Expires` datetime NOT NULL,
    `Session_Data` text COLLATE utf8_unicode_ci,
    PRIMARY KEY (`Session_Id`)
    ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
    SELECT * FROM mydatabase.Session;

    <?php
    //inc.session.php

    class SysSession implements SessionHandlerInterface
    {
    private     $link;

    public function     open($savePath, $sessionName)
    {
    $link = mysqli_connect("server","user","pwd","mydatabase");
    if(    $link){
    $this->link = $link;
    return     true;
    }else{
    return     false;
    }
    }
    public function     close()
    {
    mysqli_close($this->link);
    return     true;
    }
    public function     read($id)
    {
    $result = mysqli_query($this->link,"SELECT Session_Data FROM Session WHERE Session_Id = '".$id."' AND Session_Expires > '".date('Y-m-d H:i:s')."'");
    if(    $row = mysqli_fetch_assoc($result)){
    return     $row['Session_Data'];
    }else{
    return     "";
    }
    }
    public function     write($id, $data)
    {
    $DateTime = date('Y-m-d H:i:s');
    $NewDateTime = date('Y-m-d H:i:s',strtotime($DateTime.' + 1 hour'));
    $result = mysqli_query($this->link,"REPLACE INTO Session SET Session_Id = '".$id."', Session_Expires = '".$NewDateTime."', Session_Data = '".$data."'");
    if(    $result){
    return     true;
    }else{
    return     false;
    }
    }
    public function     destroy($id)
    {
    $result = mysqli_query($this->link,"DELETE FROM Session WHERE Session_Id ='".$id."'");
    if(    $result){
    return     true;
    }else{
    return     false;
    }
    }
    public function     gc($maxlifetime)
    {
    $result = mysqli_query($this->link,"DELETE FROM Session WHERE ((UNIX_TIMESTAMP(Session_Expires) + ".$maxlifetime.") < ".$maxlifetime.")");
    if(    $result){
    return     true;
    }else{
    return     false;
    }
    }
    }
    $handler = new SysSession();
    session_set_save_handler($handler, true);
    ?>

    <?php
    //page 1
    require_once('inc.session.php');

    session_start();

    $_SESSION['var1'] = "My Portuguese text: SOU Gaucho!";
    ?>

    <?php
    //page 2
    require_once('inc.session.php');

    session_start();

    if(isset(    $_SESSION['var1']){
    echo     $_SESSION['var1'];
    }
    //OUTPUT: My Portuguese text: SOU Gaucho!
    ?>
    up
    4
    ohcc at 163 dot com
    6 years ago
    What is not documented is that callables $validate_sid and $update_timestamp are supported since PHP 7.0. for the
    prototype of "bool session_set_save_handler ( callable $open , callable $close , callable $read , callable $write , callable $destroy , callable $gc [, callable $create_sid [, callable $validate_sid [, callable $update_timestamp ]]] )".

    validate_sid($sessionId)
    This callback is to validate $sessionId. Its return value should be true for valid session id $sessionId or false for invalid session id $sessionId. If false is returned, a new session id is generated to replace the invalid session id $sessionId.

    update_timestamp($sessionId)
    This call back is to update timestamp, and its return value should be true for success or false for failure.

    If you use this prototype, if you provide less than 6 parameters or if you provide more parameters than session_set_save_handler() accepts, you will get a "Wrong parameter count for session_set_save_handler()" warning.

    If you use the OOP prototype of session_set_save_handler(SessionHandlerInterface $sessionhandler [, bool $register_shutdown = true ] ), a member method named neither validate_sid nor update_timestamp of the class of $sessionhandler are not invoked even in PHP 7.2, but a member method named create_sid is supported as of PHP 5.5.1.

    It's 16th December, 2017 today, the documetation even PHP may get updated sometime afterwards.
    up
    3
    peter at brandrock dot co dot za
    6 years ago
    If saving to a database, as in the examples on this page, for performance, consider the following.

    Build the Sessions table with an index on the SessionExpires column to quickly identify rows to be deleted in the garbage collection phase.

    Rather do a garbage collection "delete from sessions where expiresOn < $now" on every session start/open. If you have an index on expiry time, this will not be a big hit, and evens out the load across all users. If it is possible that a large number of sessions will expire at the same time, include a "limit 100" clause, set for whatever number is reasonable, so that each user shares the load.

    Use a varchar rather than Text to store the data, as Text will store the column off-page and is retrieved slightly slower. Use Text only if your application really does store large amounts of text in the session.
    up
    14
    ohcc at 163 dot com
    6 years ago
    As of PHP 7.0, you can implement SessionUpdateTimestampHandlerInterface to
    define your own session id validating method like validate_sid and the timestamp updating method like update_timestamp in the non-OOP prototype of session_set_save_handler().

    SessionUpdateTimestampHandlerInterface is a new interface introduced in PHP 7.0, which has not been documented yet. It has two abstract methods: SessionUpdateTimestampHandlerInterface :: validateId($sessionId) and SessionUpdateTimestampHandlerInterface :: updateTimestamp($sessionId, $sessionData).

    <?php
    /*
    @author Wu Xiancheng
    Code structure for PHP 7.0+ only because SessionUpdateTimestampHandlerInterface is introduced in PHP 7.0
    With this class you can validate php session id and update the timestamp of php session data
    with the OOP prototype of session_set_save_handler() in PHP 7.0+
    */
    class PHPSessionXHandler implements SessionHandlerInterface, SessionUpdateTimestampHandlerInterface {
    public function     close(){
    // return value should be true for success or false for failure
    // ...
    }
    public function     destroy($sessionId){
    // return value should be true for success or false for failure
    // ...
    }
    public function     gc($maximumLifetime){
    // return value should be true for success or false for failure
    // ...
    }
    public function     open($sessionSavePath, $sessionName){
    // return value should be true for success or false for failure
    // ...
    }
    public function     read($sessionId){
    // return value should be the session data or an empty string
    // ...
    }
    public function     write($sessionId, $sessionData){
    // return value should be true for success or false for failure
    // ...
    }
    public function     create_sid(){
    // available since PHP 5.5.1
    // invoked internally when a new session id is needed
    // no parameter is needed and return value should be the new session id created
    // ...
    }
    public function     validateId($sessionId){
    // implements SessionUpdateTimestampHandlerInterface::validateId()
    // available since PHP 7.0
    // return value should be true if the session id is valid otherwise false
    // if false is returned a new session id will be generated by php internally
    // ...
    }
    public function     updateTimestamp($sessionId, $sessionData){
    // implements SessionUpdateTimestampHandlerInterface::validateId()
    // available since PHP 7.0
    // return value should be true for success or false for failure
    // ...
    }
    }
    ?>
    up
    3
    polygon dot co dot in at gmail dot com
    3 years ago
    Below is a demo to check the order in which session function executes.

    <?php

    ini_set    ('session.use_strict_mode',true);

    function     sess_open($sess_path, $sess_name) {
    echo     '<br/>sess_open';
    return     true;
    }

    function     sess_close() {
    echo     '<br/>sess_close';
    return     true;
    }

    function     sess_read($sess_id) {
    echo     '<br/>sess_read';
    return     '';
    }

    function     sess_write($sess_id, $data) {
    echo     '<br/>sess_write';
    return     true;
    }

    function     sess_destroy($sess_id) {
    echo     '<br/>sess_destroy';
    return     true;
    }

    function     sess_gc($sess_maxlifetime) {
    echo     '<br/>sess_gc';
    return     true;
    }

    function     sess_create_sid() {
    echo     '<br/>sess_create_sid';
    return     'RNS'.rand(0,10);
    }

    function     sess_validate_sid($sess_id) {
    echo     '<br/>sess_validate_sid';
    return     true;
    }

    function     sess_update_timestamp($sess_id,$data) {
    echo     '<br/>sess_update_timestamp';
    return     true;
    }

    session_set_save_handler(
    'sess_open',
    'sess_close',
    'sess_read',
    'sess_write',
    'sess_destroy',
    'sess_gc',
    'sess_create_sid',
    'sess_validate_sid',
    'sess_update_timestamp'
    );

    session_start();

    echo     '<br/>code here...';

    ?>

    O/P Below when above code executed first time.
    sess_open
    sess_create_sid
    sess_read
    code here...
    sess_write
    sess_close

    O/P Below for next execution.
    sess_open
    sess_validate_sid
    sess_read
    code here...
    sess_write
    sess_close
    up
    5
    Steven George
    10 years ago
    Note that as well as destructing objects before calling write() and close(), it seems PHP also destroys classes. That is, you can't even call a static method of an external class in the write() and close() handlers - PHP will issue a Fatal error stating "Class xxxx not found"
    up
    3
    tomas at slax dot org
    16 years ago
    Regarding the SAPIs: The warning mentioned in function's description (that the Current working directory is changed with some SAPIs) is very important.

    It means that if your callback 'write' function needs to write to a file in current directory, it will not find it. You have to use absolute path and not rely upon the current working directory.

    I thought this warning applies only to some strange environments like Windows, but it happens exactly on Linux + Apache 2.2 + PHP 5.
    up
    2
    tony at marston-home dot demon dot co dot uk
    6 years ago
    Your custom session handler should not contain calls to any of the session functions, such as session_name() or session_id(), as the relevant values are passed as arguments on various handler methods. Attempting to obtain values from alternative sources may not work as expected.
    up
    2
    centurianii at yahoo dot co dot uk
    7 years ago
    Adding to the very useful class from: andreipa at gmail dot com

    1. You should handle session expiration & data I/O from the SessionHandlerInterface methods,
    2. You should NOT handle session regeneration and data modification from these methods but from a static method, e.g. sth like Session::start().
    3. PHP gives a lot of examples but does NOT say what's the perspective under which one should work.

    A skeleton of such a class:
    namespace xyz;
    class Session implements \SessionHandlerInterface, Singleton {
    /** @var SessionToken $token The SessionToken of this command;
    this is part of my programming approach */
    protected $token;
    /** @var PDO $dbh The PDO handler to the database */
    protected $dbh;
    /** @var $savePath Where sessions are stored */
    protected $savePath;
    /** @var $type Type of sessions (['files'|'sqlite']) */
    protected $type;
    /** @var self $instance An instance of this class */
    static private $instance = null;

    private function __construct() { ... }
    static public function getInstance() {
    if (self::$instance === null) {
    self::$instance = new self();
    }
    return self::$instance;
    }
    public function open($savePath, $sessionName) { ... }
    public function close() {
    if ($this->type == static::FILES) {
    return true;
    } elseif ($this->type == static::SQLITE) {
    return true;
    }
    }
    public function read($id) { ... }
    public function write($id, $data) { ... }
    public function destroy($id) { ... }
    public function gc($maxlifetime) { ... }
    static public function get($key) {
    return (isset($_SESSION[$key]))? $_SESSION[$key] : null;
    }
    static public function set($key, $value) {
    return $_SESSION[$key] = $value;
    }
    static public function newId() {...}
    static public function start($call = null, $log = false) {
    //1. start session (send 1st header)
    if (session_status() != PHP_SESSION_ACTIVE) {
    session_start(); //calls: open()->read()
    }

    //2. $_SESSION['session']: array of session control data
    // existed session
    if (is_array(static::get('session'))) {
    $session = static::get('session');
    // new session
    } else {
    $session = array();
    }

    $tmp = $_SESSION;
    //do sth with $session array...
    static::set('session', $session);
    session_write_close(); //calls: write()->read()->close()
    //create a new session inside if...else...
    session_id(static::newId());
    session_start(); //calls: open()->read()
    //if you want previous session data to be copied:
    //$_SESSION = $tmp;
    //do sth else with $session array and save it to new session...
    static::set('session', $session);

    //6. call callback function (only on valid/new sessions)
    if ($call)
    $call();
    session_write_close(); //calls: write()->read()->close()
    }
    /**
    * Defines custom session handler.
    */
    static public function setHandler() {
    // commit automatic session
    if (ini_get('session.auto_start') == 1) {
    session_write_close();
    }
    $handler = static::getInstance();
    session_set_save_handler($handler, true);
    }
    }

    Let's start a session:
    Session::setHandler();
    Session::start();

    Trying for hours to trace my error where the 3rd Session::read() ended to use a null Session::dbh until I realized that Session::close() should NOT destroy properties of this class!
    Also I avoid the use of session_create_id() as it's only for PHP 7 >= 7.1.0 and I use in place a static Session::newId().
    up
    2
    shanikawm at gmail dot com
    8 years ago
    Here is a class to handle session using an Oracle table.
    https://github.com/shanikawm/PHP_Oracle_Based_Session_Handler_Class

    <?php
    /**
    * By Shanika Amarasoma
    * Date: 6/24/2016
    * PHP session handler using Oracle database
    * Oracle Create table statement
    CREATE TABLE PHP_SESSIONS
    (
    SESSION_ID VARCHAR2(256 BYTE) UNIQUE,
    DATA CLOB,
    TOUCHED NUMBER(38)
    );
    */
    class session_handler implements SessionHandlerInterface
    {
    private     $con;
    public function     __construct() {
    if(!    $this->con=oci_pconnect(DBUSER,DBPASS,CONNECTION_STR)){
    die(    'Database connection failed !');
    }
    }
    public function     open($save_path ,$name){
    return     true;
    }
    public function     close(){
    return     true;
    }
    public function     read($session_id){
    $query = "SELECT \"DATA\" FROM PHP_SESSIONS WHERE SESSION_ID=Q'{" . $session_id . "}'";
    $stid = oci_parse($this->con, $query);
    oci_execute($stid, OCI_DEFAULT);
    $row = oci_fetch_array($stid, OCI_ASSOC + OCI_RETURN_LOBS);
    oci_free_statement($stid);
    return     $row['DATA'];
    }
    public function     write($session_id,$session_data){
    $dquery="DELETE FROM PHP_SESSIONS WHERE SESSION_ID=Q'{".$session_id."}'";
    $dstid = oci_parse($this->con,$dquery);
    oci_execute($dstid, OCI_NO_AUTO_COMMIT);
    oci_free_statement($dstid);
    $query="INSERT INTO PHP_SESSIONS(SESSION_ID,TOUCHED,\"DATA\") VALUES(Q'{".$session_id."}',".time().",EMPTY_CLOB()) RETURNING \"DATA\" INTO :clob";
    $stid = oci_parse($this->con,$query);
    $clob=oci_new_descriptor($this->con,OCI_D_LOB);
    oci_bind_by_name($stid, ':clob', $clob, -1, OCI_B_CLOB);
    if(!    oci_execute($stid, OCI_NO_AUTO_COMMIT)){
    @    oci_free_statement($stid);
    return     false;
    }
    if(    $clob->save($session_data)){
    oci_commit($this->con);
    $return=true;
    } else {
    oci_rollback($this->con);
    $return=false;
    }
    $clob->free();
    oci_free_statement($stid);
    return     $return;
    }
    public function     destroy($session_id){
    $query="DELETE FROM PHP_SESSIONS WHERE SESSION_ID=Q'{".$session_id."}'";
    $stid = oci_parse($this->con,$query);
    oci_execute($stid, OCI_DEFAULT);
    $rows=oci_num_rows($stid);
    oci_commit($this->con);
    oci_free_statement($stid);
    if(    $rows>0){
    return     true;
    } else {
    return     false;
    }
    }
    public function     gc($maxlifetime){
    $query="DELETE FROM PHP_SESSIONS WHERE TOUCHED<".(time()-$maxlifetime);
    $stid = oci_parse($this->con,$query);
    oci_execute($stid, OCI_DEFAULT);
    $rows=oci_num_rows($stid);
    oci_commit($this->con);
    oci_free_statement($stid);
    if(    $rows>0){
    return     true;
    } else {
    return     false;
    }
    }
    }
    session_set_save_handler(new session_handler(), true);
    session_start();
    up
    2
    korvus at kgstudios dot net
    19 years ago
    It seems when you call 'session_name()', php loads the session id automatically from GET ( if the index exists ) and passes it to the 'read' callback method correctly, but the 'write' callback is invoked twice: first the auto-generated session id, then the custom session id

    So be aware of what queries you execute inside the callback .. I got crazy because I used a MySQL 'REPLACE' statement to agilize, and I spent a lot of hours trying to understand why 2 rows instead of 1 were being affected ( the first id was inserting, the second updating )

    I hope this helps!
    up
    3
    ivo at magstudio dot net
    21 years ago
    Just a few words to explain some troubles while using session_set_save_handler(). It appears that internally PHP calls session management functions in this order: open(), read(), write(), close(). Close() function is called even if you does not make a call to sesison_start(), perhaps for some reasons like cleaning.
    If you try to redefine these functions and call sessions_set_save_handler() but something doesn't work, (in my case the ssion data hasn't been written) it's a good idea to debug them in the order they are called. They doesn't produce error output to browser but you can use print or echo.
    Shortly, if your write() function doesn't work as expected take a look for errors in previous functions - open() and read().
    I hope that this will help to save someone few hours debugging.
    up
    5
    oliver at teqneers dot de
    19 years ago
    For some people it might be important to know, that if the standard session handler has been overwritten with session_set_save_handler, no locking is working anymore (between session_read and session_write). The following might happen:

    script "A" start .
    read session data .
    . script "B" start
    . read session data
    running (30secs) add session data
    . write sesion data
    . script "B" stop
    write session data .
    script "A" stop .

    If a script "A" runs for a long time (say 30secs) the same user might start another script "B", which also uses a session. Script "B" will start and read session data, even though script "A" is still running. Because script "B" is much faster it will finish its work and write back its session data before script "A" has ended. Now script "A" ends and overwrites all of script "B"'s session data. If you DON'T use session_set_save_handler, this cannot happend, because in this case, PHP will not start script "B" until script "A" ends.
    up
    4
    e dot sand at elisand dot com
    15 years ago
    The "binary" data that is in the session data appears to surround class/object names, and if you pass your session data through a function to sanitize it for SQL injection, you may indeed run in to problems.

    For example, using the PDO::quote() function to prepare the data for injection (in my case for SQLite3), it was stopping short as soon as it encountered the first bit of binary data, causing my session information to be corrupted.

    This change *must* have happened somewhere in the 5.2 series, because I just started encountering this problem recently on a code base that had been tested & working on earlier versions of PHP 5.2.

    This may in fact be a bug - I have not yet checked... but beware, and perhaps using base64 to encode/decode your session data is a good thing to do just to be sure (though you are now left unable to visually inspect serialized session information at the storage level which is a rather big problem for on-the-fly debugging of sessions).
    up
    4
    james at dunmore dot me dot uk
    17 years ago
    I think it is very important here to stress that the WRITE method should use UPDATE+INSERT (or mysql specific REPLACE).

    There is example code "out there" that uses just UPDATE for the write method, in which case, when session_regenerate_id is called, session data is lost (as an update would fail, as the key has changed).

    I've just wasted a whole day due to this (I know I should have thought it through / RTFM, but it is an easy trap to fall into).
    up
    3
    frank at interactinet dot com
    13 years ago
    I had trouble with committing session data.
    To "commit and continue" without closing your session, put this at the top of your "write" method:

    <?php

    $id     = session_id();
    session_write_close();
    session_id($id);
    session_start();

    ?>

    Note that ANY time php generates a new session id, it is not automatically updated in a database. This can be helpful:

    <?php

    public function resetSessionId()
    {
    $old = session_id();
    session_regenerate_id();
    $new = session_id();
    SessionHandler::regenerate_id($old,$new);
    }

    public function     regenerate_id($old,$new)
    {
    $db = mysqli->connect(...);

    $db->query('UPDATE sessions SET session_id = \''.$db->escape_string($new).'\'
    WHERE session_id = \''    .$db->escape_string($old).'\'');
    }
    ?>
    up
    4
    carlos dot vini at gmail dot com
    8 years ago
    If you have a custom handler registered ini_get('session.save_handler') will return 'user' instead of 'file'
    up
    5
    matt at openflows dot org
    18 years ago
    Note that for security reasons the Debian and Ubuntu distributions of php do not call _gc to remove old sessions, but instead run /etc/cron.d/php*, which check the value of session.gc_maxlifetime in php.ini and delete the session files in /var/lib/php*. This is all fine, but it means if you write your own session handlers you'll need to explicitly call your _gc function yourself. A good place to do this is in your _close function, like this:

    <?php
    function _close() {
    _gc(get_cfg_var("session.gc_maxlifetime"));
    // rest of function goes here
    }
    ?>
    up
    2
    dummynick at gmail dot com
    14 years ago
    I was getting Fatal error: Exception thrown without a stack frame and it took days to figure out the reason. I am using memcache to store sessions and in my custom class I use Memcache class in write method.

    I put the code in the write method inside try-catch block and it solved my problem.
    up
    2
    joel the usual at sign then purerave.com
    14 years ago
    When storing sessions in a DB, it's usually beneficial to use an existing custom DB object, but this creates problems with the latest version of PHP 5.3.1. This used to work fine on PHP 5.2.x (Linux and Windows).

    The problem now is that session_write_close() is not automatically called when execution ends, but rather after all the objects have been destructed, including the DB object!

    There are two ways around this, either manually calling session_write_close() at the end of your script(s), or not using the DB object.

    I'm sure this is the intended behavior from the beginning.
    up
    4
    yangqingrong at gmail dot com
    15 years ago
    session_set_save_handler is used before session_start.if your session is setted as auto start. it will return FALSE value.so you need add session_write_close() before session_set_save_handler to cancel the session's auto start.it likes this:

    <?php
    /*
    qq:290359552
    */
    session_write_close(); //cancel the session's auto start,important

    function open()
    {
    ...
    }
    ....
    session_set_save_handler( ... );
    session_start();
    ?>
    up
    1
    bart2yk at yahoo dot com
    14 years ago
    You can call the session_write in db object destructor to be shore that you still have a connection to mysql and the session is write.
    up
    1
    sneakyimp AT hotmail DOT com
    18 years ago
    the behavior, return values, and exact time of calling for these functions is pretty poorly documented here. i thought folks might like to know that:

    1) calling session_start() triggers PHP to first call your open function and then call your read function before resuming with the code immediately following your session_start() call.

    2) calling session_id('some_value') within your open function WILL NOT SET THE SESSION COOKIE (at least not on my setup - PHP 4.4.1). Assuming you defined some function to validate a session id called my_func(), you might want to do something like this in your open function:

    <?php
    function _open($save_path, $session_name) {
    // check for session id
    $sess_id = session_id();
    if (empty(    $sess_id) || !myfunc($sess_id)) {
    //session_id is INVALID - generating new
    $new_id = md5(uniqid("some random seed here"));
    session_id($new_id);
    setcookie(session_name(),
    $new_id,
    0,
    "/",
    ".mydomain.com");
    }

    return     true;
    }     // _open()
    ?>
    up
    5
    harald at hholzer at
    15 years ago
    after spending 8 hours to find out whats going on..

    just for the records, because php.net ignore the real world out there:

    debian 5 installs by default the php-suhosin module, which changes the behavior of session_set_save_handler read/write function.

    on calling the session write function the session data will be encrypted, and the returning string from the read function are decrypted and verified.

    the encrypted data is no more compatible with session_encode/session_decode.

    and breaks by default, subdomain handling and multiple host setups where different document roots are used.

    for futher information look at:
    http://www.hardened-php.net/suhosin/configuration.html

    session sample data (debian 4):
    test|s:3:"sdf";

    session sample data (debian 5, with php-suhosin):
    3GdlPEGr2kYgRFDs-pUSoKomZ4fN7r5BM5oKOCMsWNc...

    i thing the suhosin patch should report a warning in case of invalid session data, to get a clue whats going wrong.
    up
    2
    james dot ellis at gmail dot com
    16 years ago
    When writing your own session handler, particularly database session handlers, play close attention to garbage cleanup and how it could affect server load.

    To pick a round number example:

    If you have 1000 requests per minute on session enabled pages, everyone needs a session started but the session garbage cleanup does not need to run every request. Doing so would cause unrequired queries on the database server.

    In this example, setting your probability/divisor to 1/1000 would be sufficient to clean up old sessions at a minimum once a minute. If you don't need that kind of granularity, increase the gc divisor.

    Finding the tradeoff between clearing up old sessions and server load is the important aspect here.
    up
    2
    information at saunderswebsolutions dot com
    18 years ago
    Note that if session.auto_start is set to On in the php.ini, your session_set_save_handler will return false as the session has already been initialized.

    If you are finding that your code works OK on one machine but doesn't work on another, check to see if session.auto_start is set to On
    up
    2
    Rusty X
    12 years ago
    It is important to understand that PHP's default file-based session handling LOCKS the session file, inherently allowing ONLY ONE thread handling any given session at a time.
    When you implement a DB-backed session storage and you do not do any locking, you may run into situations where more than one thread is serving the same session, and you may LOSE DATA because the second thread will overwrite any session changes done by the first thread.
    You should therefore think about locking the session somehow if you want to have the exact same behavior as with the default file-based implementation. For example, with InnoDB you could do a SELECT ... FOR UPDATE, or you can use the GET_LOCK() function.
    up
    1
    Balu
    20 years ago
    If a session is closed the save-handlers seem to be resetted (in PHP 4.1.2 they are), so you need to run session_set_save_handler() again after e.g. running session_write_close() and restarting the session with session_start();
    up
    1
    skds1433 at hotmail dot com
    15 years ago
    I pulled a really stupid move. If you are trying to debug your garbage collector, make sure you call the following >>> BEFORE <<< "session_start":

    <?php
    ini_set    ('session.gc_probability', 100);
    ini_set('session.gc_divisor', 100);
    ?>

    I was sure it was a bug in PHP, but turned out (like 99% of the time) to be me own fault.
    up
    1
    biba dot vasyl at gmail dot com
    9 months ago
    if you use the interface (SessionHandlerInterface) to implement the storage of the session in the mysql database, it is not clear what the read method should return, because the return is specified in the interface: string|false, that is, if I refer to the type:
    public function read(string $id): string|false {
    if ($id) {
    $sql = "SELECT `session_id`, `data` FROM `session` WHERE `session_id` = '" . $this->db->escape($id) . "'";
    pp($sql);
    $query = $this->db->query($sql);
    if ($query->num_rows) {
    //return (isset($query->one['data']) ? (array)json_decode($query->one['data'], true) : []);
    return $query->one['session_id'];
    } else {
    return '';
    }
    }
    return false;
    }
    ref.: https://www.php.net/manual/ru/sessionhandlerinterface.read.php
    then I will receive an error response of the following plan: Error #: 2, message: session_start(): Failed to decode session object. Session has been destroyed
    up
    1
    polygon dot co dot in at gmail dot com
    1 year ago
    Although, session_set_save_handler() has support for saving session data via other modes, This does not support a way for saving session data in COOKIES. This is required for a site with a huge concurrent request the recommended solution by session_set_save_handler() does not fit the load site is handling.
    So, the other way around to do this is as below.

    <?php
    // start.php
    ob_start(); // Turn on output buffering

    $sessCookieName = session_name();
    $_SESSION = json_decode(base64_decode($_COOKIE[$sessCookieName]), true);

    // Code
    function echosess() {
    echo     $_SESSION['id'];
    }
    echosess();
    $_SESSION['id'] = 1;

    // end.php
    $op = ob_get_clean(); // Get current buffer contents and delete current output buffer
    $encryptedData = base64_encode(json_encode($_SESSION));
    setcookie($sessCookieName, $encryptedData, time() + (ini_get("session.gc_maxlifetime")), '/');
    echo     $op;
    ?>

    If more security is required about the data of the session in cookie, then key based encryption/decryption can solve the issue.
    up
    2
    dimzon541 at gmail dot com
    9 years ago
    Persisting PHP sessions into mongodb (allows NLB without affinity)
    https://gist.github.com/dimzon/62eeb9b8561bcb9f0c6d
    up
    0
    polygon dot co dot in at gmail dot com
    3 months ago
    Sessions data can be saved in different modes eg; Files, SQL and No SQL databases.

    But while benchmarking session it is observed File based session leads to depletion of inodes, SQL databases leads to slower performance due to large number of indexed session ids and no SQL databases leads to performance issues.

    Benchmarking session is simulating session behaviour on attacks that may bring down a website or effect website performance.

    As a solution to this on can start the session as below in the common file.

    if ( isset( $_COOKIE['PHPSESSID'] ) ) {
    // Wrong cookie values won't create a new session file/entry.
    // Because its a read only.
    session_start(
    [
    'read_and_close' => true,
    ]
    );
    }

    This will start a read only session.

    Once you are done with this and later in script you need to make changes (add/remove) session data. One can start the session in the normal way which we used to do earlier.

    session_start();

    and do required modifications.

    $_SESSION[‘’key] = $value;

    OR

    unset($_SESSION[‘’some_key]);
    up
    0
    polygon dot co dot in at gmail dot com
    1 year ago
    How to use Cookie for managing session data with encryption.

    <?php
    class MySessionHandler implements SessionHandlerInterface
    {
    function     __construct()
    {
    // Store the key and IV somewhere safe
    //$key = openssl_random_pseudo_bytes(32); // 256-bit key
    //$iv = openssl_random_pseudo_bytes(16); // 128-bit IV

    // Store the base64 key and IV somewhere safe
    //$key_base64 = base64_encode($key);
    //$iv_base64 = base64_encode($vi);

    // Use the store base64 key and IV below
    $key_base64 = 's8Livn/jULM6HDdPY76E3aXtfELdleTaqOC8HgTfW7M=';
    $iv_base64 = 'nswqKP23TT+deVNuaV5nXQ==';
    $this->key = base64_decode($key_base64);
    $this->iv = base64_decode($iv_base64);
    }

    // Encryption
    function encryptSess($plaintext)
    {
    return     openssl_encrypt($plaintext, 'AES-256-CBC', $this->key, OPENSSL_RAW_DATA, $this->iv);
    }

    // Decryption
    function decryptSess($ciphertext)
    {
    return     openssl_decrypt($ciphertext, 'AES-256-CBC', $this->key, OPENSSL_RAW_DATA, $this->iv);
    }

    public function     open($savePath, $sessionName): bool
    {
    ob_start(); // Turn on output buffering
    return true;
    }

    public function     close(): bool
    {
    return     true;
    }

    #[    \ReturnTypeWillChange]
    public function     read($id)
    {
    if (isset(    $_COOKIE[session_name()])) {
    return (string)    $this->decryptSess(base64_decode($_COOKIE[session_name()]));
    } else {
    return     '';
    }
    }

    public function     write($id, $data): bool
    {
    $op = ob_get_clean();
    $encryptedData = base64_encode($this->encryptSess($data));
    setcookie(session_name(), $encryptedData, time() + (ini_get("session.gc_maxlifetime")), '/');
    echo     $op;

    return     true;
    }

    public function     destroy($id): bool
    {
    return     true;
    }

    #[    \ReturnTypeWillChange]
    public function     gc($maxlifetime)
    {
    return     true;
    }
    }

    $handler = new MySessionHandler();
    session_set_save_handler($handler, true);
    session_start();
    var_dump($_SESSION);
    $_SESSION['id'] = 10000;

    echo     '<br/>Hello World';
    ?>
    up
    1
    nickleus
    7 years ago
    i dont see any mention of what happens when eg "open" calls "die", like mentioned in docs for "register_shutdown_function":

    "If you call exit() within one registered shutdown function, processing will stop completely and no other registered shutdown functions will be called."

    http://php.net/manual/en/function.register-shutdown-function.php

    my result: same behavior--"read" will not get called if "open" calls "die"/"exit".
    up
    0
    jamesbenson944 at hotmail dot com
    11 years ago
    I'm not using objects for the save handlers I'm using functions but still get weird behaviour with session writing not being called.

    This fixes the problem though:
    register_shutdown_function('session_write_close');
    up
    0
    anonymous at anonymous dot org
    16 years ago
    if you simply append the information from session variables every time you'll have many multiples for variables each time they are changed. a simple way to do this is explode the data twice to seperate the variable name from the other relevant information and foreach() check against the stored set. here is a little bit of a mess i wrote to do it.
    assuming stored session variables in both database and passed through function:

    <?php
    $buffer     = array();
    $buffer = explode('|',$sessiondata);
    $buf1 = array();
    $buf2 = array();
    $finalbuff = '';
    foreach(    $buffer as $i){
    $i = explode(';',$i);
    foreach(    $i as $b){
    array_push($buf1,$b);
    }
    }
    $buffer = explode('|',$result['data']);
    foreach(    $buffer as $i){ $i = explode(';',$i); foreach($i as $b){ array_push($buf2,$b);}}
    $z = 0;
    $x = 0;
    while(    $buf2[$z]){
    while(    $buf1[$x]){
    if(    $buf2[$z] == $buf1[$x]){
    $buf2[($z+1)] = $buf1[($x+1)];
    }
    $x+=2;
    }
    $z+=2;
    }
    foreach(    $buf2 as $i){ $finalbuff .= $i; }
    ?>

    $sessiondata is the variable passed through the function and $result['data'] is the data stored in an sql database.
    up
    0
    Colin
    17 years ago
    When using a custom session handler, if the first callback function (sessOpen in my case) finds no session id, one is set by the time the second argument (sessRead in my case) is called.
    up
    0
    mjohnson at pitsco dot com
    18 years ago
    With regards to the read handler, the docs say:

    "Read function must return string value always to make save
    handler work as expected. Return empty string if there is no
    data to read."

    I can't emphasize this enough. I just spent half a day trying to figure out why my sessions weren't storing any information. I was blithely returning the results of a query on the database from the read handler. Since there was no match for the new ID, the result was NULL. Since it wasn't a string, sessions were essentially disabled. So, the safe thing might be something like this:

    <?php
    function sessRead($id)
    {
    // Look up data
    $results = getStuff($id);

    // Make sure it's a string
    settype($results, 'string');
    return     $results;
    }
    ?>

    Of course, you can do whatever you want with it. But, no matter what, make sure you return a string.

    HTH,
    Michael
    up
    0
    coco at digitalco2 dot com
    20 years ago
    When using mySQL for your session handling functions, don't forget to call mysql_select_db() to change the database if you are using a separate database for your session data. Call mysql_select_db() INSIDE every handler function that accesses the database, since if you write session data after accessing another database, it will not change the database to your session database, and therefore, not write the session data.
    up
    0
    spam at skurrilo dot de
    22 years ago
    You can't use the session autostart feature with

    session.save_handler = user

    set in your php.ini. Use instead the auto_prepend_file directive in the php.ini and point it to your save_handler with an session_start() at the end.
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