The SessionHandlerInterface class

    (PHP 5 >= 5.4.0, PHP 7, PHP 8)

    Introduction

    SessionHandlerInterface is an interface which defines the minimal prototype for creating a custom session handler. In order to pass a custom session handler to session_set_save_handler() using its OOP invocation, the class can implement this interface.

    Please note the callback methods of this class are designed to be called internally by PHP and are not meant to be called from user-space code.

    Interface synopsis

    interface SessionHandlerInterface {
    /* Methods */
    public close(): bool
    public destroy(string $id): bool
    public gc(int $max_lifetime): int|false
    public open(string $path, string $name): bool
    public read(string $id): string|false
    public write(string $id, string $data): bool
    }

    Examples

    Example #1 Example using SessionHandlerInterface

    The following example provides file based session storage similar to the PHP sessions default save handler files. This example could easily be extended to cover database storage using your favorite PHP supported database engine.

    Note we use the OOP prototype with session_set_save_handler() and register the shutdown function using the function's parameter flag. This is generally advised when registering objects as session save handlers.

    Caution

    For brevity, this example omits input validation. However, the $id parameters are actually user supplied values which require proper validation/sanitization to avoid vulnerabilities, such as path traversal issues. So do not use this example unmodified in production environments.

    <?php
    class MySessionHandler implements SessionHandlerInterface
    {
    private     $savePath;

    public function     open($savePath, $sessionName): bool
    {
    $this->savePath = $savePath;
    if (!    is_dir($this->savePath)) {
    mkdir($this->savePath, 0777);
    }

    return     true;
    }

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

    #[    \ReturnTypeWillChange]
    public function     read($id)
    {
    return (string) @    file_get_contents("$this->savePath/sess_$id");
    }

    public function     write($id, $data): bool
    {
    return     file_put_contents("$this->savePath/sess_$id", $data) === false ? false : true;
    }

    public function     destroy($id): bool
    {
    $file = "$this->savePath/sess_$id";
    if (    file_exists($file)) {
    unlink($file);
    }

    return     true;
    }

    #[    \ReturnTypeWillChange]
    public function     gc($maxlifetime)
    {
    foreach (    glob("$this->savePath/sess_*") as $file) {
    if (    filemtime($file) + $maxlifetime < time() && file_exists($file)) {
    unlink($file);
    }
    }

    return     true;
    }
    }

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

    // proceed to set and retrieve values by key from $_SESSION

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    User Contributed Notes 8 notes

    up
    21
    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
    4
    ohcc at 163 dot com
    6 years ago
    The non-OOP prototype of session_set_save_handler() supports validate_sid and update_timestamp as of PHP 7.0 while the OOP prototype doesn't even in PHP 7.2. However the OOP prototype does support create_sid since PHP 5.5.1.

    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.
    up
    1
    ohcc at 163 dot com
    6 years ago
    As of PHP 5.5.1, another method create_sid() is supported. It will be called when session_regenerate_id() is invoked.

    SessionHandlerInterface {
    /* Methods */
    abstract public bool close ( void )
    abstract public bool create_sid ( void )
    abstract public bool destroy ( string $session_id )
    abstract public bool gc ( int $maxlifetime )
    abstract public bool open ( string $save_path , string $session_name )
    abstract public string read ( string $session_id )
    abstract public bool write ( string $session_id , string $session_data )
    }
    up
    5
    warxcell at gmail dot com
    12 years ago
    You should prepend <b>\</b> before class name, to tell php its from root namespace.
    up
    3
    avenidagez at foro5 dot com
    9 years ago
    Note that session_start( ) calls open then read and the class returns true for open and the value of session or empty for read.
    Well, then there is no catch for errors, this is, session_start() must return false on failure, but that is not the case for the class implementation on method open, no matter if you return true or false or whatever from open, it is ignored by session_start() function and proceeds to read method
    A bug?, if open returns false, session_start() should stop the next step (read) and return itself false

    if(session_start()) ...code
    else exit( );

    So forget about session_start() return value, you need to implement an error catch routine and exit() in case of failure on open method
    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
    0
    ohcc at 163 dot com
    4 years ago
    If you want to use type declarations in your own session handling class, don't "implements" the SessionHandlerInterface, SessionIdInterface, or SessinUpdateTimestampInterface, otherwise you will get a fatal error saying that declaration of the class method must be compatible with the interface method.

    a bad example
    <?php
    class SessionWuXianchengHandler implements SessionHandlerInterface {
    public function     open(string $sessionPath, string $sessionName) : bool {
    }
    ......
    }
    ?>

    a good example
    <?php
    class SessionWuXianchengHandler {
    public function     open(string $sessionPath, string $sessionName) : bool {
    }
    ......
    }
    ?>
    up
    -3
    StanE
    9 years ago
    I think there is a small "error" in the example of the class MySessionHandler in method gc(). It uses the function filemtime() whose return value is cached by PHP. Add the following line inside the foreach block in the gc() method:

    clearstatcache(true, $file);
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