root/trunk/system/libraries/Session.php

<?php
/**
 * Session library.
 *
 * $Id$
 *
 * @package    Core
 * @author     Kohana Team
 * @copyright  (c) 2007-2008 Kohana Team
 * @license    http://kohanaphp.com/license.html
 */
class Session_Core {

    // Session singleton
    private static $instance;

    // Protected key names (cannot be set by the user)
    protected static $protect = array('session_id', 'user_agent', 'last_activity', 'ip_address', 'total_hits', '_kf_flash_');

    // Configuration and driver
    protected static $config;
    protected static $driver;

    // Flash variables
    protected static $flash;

    // Input library
    protected $input;

    /**
     * Singleton instance of Session.
     */
    public static function instance()
    {
        if (self::$instance == NULL)
        {
            // Create a new instance
            new Session;
        }

        return self::$instance;
    }

    /**
     * On first session instance creation, sets up the driver and creates session.
     */
    public function __construct()
    {
        $this->input = Input::instance();

        // This part only needs to be run once
        if (self::$instance === NULL)
        {
            // Load config
            self::$config = Kohana::config('session');

            // Makes a mirrored array, eg: foo=foo
            self::$protect = array_combine(self::$protect, self::$protect);

            // Configure garbage collection
            ini_set('session.gc_probability', (int) self::$config['gc_probability']);
            ini_set('session.gc_divisor', 100);
            ini_set('session.gc_maxlifetime', (self::$config['expiration'] == 0) ? 86400 : self::$config['expiration']);

            // Create a new session
            $this->create();

            if (self::$config['regenerate'] > 0 AND ($_SESSION['total_hits'] % self::$config['regenerate']) === 0)
            {
                // Regenerate session id and update session cookie
                $this->regenerate();
            }
            else
            {
                // Always update session cookie to keep the session alive
                cookie::set(self::$config['name'], $_SESSION['session_id'], self::$config['expiration']);
            }

            // Close the session just before sending the headers, so that
            // the session cookie(s) can be written.
            Event::add('system.send_headers', array($this, 'write_close'));

            // Make sure that sessions are closed before exiting
            register_shutdown_function(array($this, 'write_close'));

            // Singleton instance
            self::$instance = $this;
        }

        Kohana::log('debug', 'Session Library initialized');
    }

    /**
     * Get the session id.
     *
     * @return  string
     */
    public function id()
    {
        return $_SESSION['session_id'];
    }

    /**
     * Create a new session.
     *
     * @param   array  variables to set after creation
     * @return  void
     */
    public function create($vars = NULL)
    {
        // Destroy any current sessions
        $this->destroy();

        if (self::$config['driver'] !== 'native')
        {
            // Set driver name
            $driver = 'Session_'.ucfirst(self::$config['driver']).'_Driver';

            // Load the driver
            if ( ! Kohana::auto_load($driver))
                throw new Kohana_Exception('core.driver_not_found', self::$config['driver'], get_class($this));

            // Initialize the driver
            self::$driver = new $driver();

            // Validate the driver
            if ( ! (self::$driver instanceof Session_Driver))
                throw new Kohana_Exception('core.driver_implements', self::$config['driver'], get_class($this), 'Session_Driver');

            // Register non-native driver as the session handler
            session_set_save_handler
            (
                array(self::$driver, 'open'),
                array(self::$driver, 'close'),
                array(self::$driver, 'read'),
                array(self::$driver, 'write'),
                array(self::$driver, 'destroy'),
                array(self::$driver, 'gc')
            );
        }

        // Validate the session name
        if ( ! preg_match('~^(?=.*[a-z])[a-z0-9_]++$~iD', self::$config['name']))
            throw new Kohana_Exception('session.invalid_session_name', self::$config['name']);

        // Name the session, this will also be the name of the cookie
        session_name(self::$config['name']);

        // Set the session cookie parameters
        session_set_cookie_params
        (
            self::$config['expiration'],
            Kohana::config('cookie.path'),
            Kohana::config('cookie.domain'),
            Kohana::config('cookie.secure'),
            Kohana::config('cookie.httponly')
        );

        // Start the session!
        session_start();

        // Put session_id in the session variable
        $_SESSION['session_id'] = session_id();

        // Set defaults
        if ( ! isset($_SESSION['_kf_flash_']))
        {
            $_SESSION['total_hits'] = 0;
            $_SESSION['_kf_flash_'] = array();

            $_SESSION['user_agent'] = Kohana::$user_agent;
            $_SESSION['ip_address'] = $this->input->ip_address();
        }

        // Set up flash variables
        self::$flash =& $_SESSION['_kf_flash_'];

        // Increase total hits
        $_SESSION['total_hits'] += 1;

        // Validate data only on hits after one
        if ($_SESSION['total_hits'] > 1)
        {
            // Validate the session
            foreach (self::$config['validate'] as $valid)
            {
                switch ($valid)
                {
                    // Check user agent for consistency
                    case 'user_agent':
                        if ($_SESSION[$valid] !== Kohana::$user_agent)
                            return $this->create();
                    break;

                    // Check ip address for consistency
                    case 'ip_address':
                        if ($_SESSION[$valid] !== $this->input->$valid())
                            return $this->create();
                    break;

                    // Check expiration time to prevent users from manually modifying it
                    case 'expiration':
                        if (time() - $_SESSION['last_activity'] > ini_get('session.gc_maxlifetime'))
                            return $this->create();
                    break;
                }
            }
        }

        // Expire flash keys
        $this->expire_flash();

        // Update last activity
        $_SESSION['last_activity'] = time();

        // Set the new data
        self::set($vars);
    }

    /**
     * Regenerates the global session id.
     * 
     * @return  void
     */
    public function regenerate()
    {
        if (self::$config['driver'] === 'native')
        {
            // Generate a new session id
            // Note: also sets a new session cookie with the updated id
            session_regenerate_id(TRUE);

            // Update session with new id
            $_SESSION['session_id'] = session_id();
        }
        else
        {
            // Pass the regenerating off to the driver in case it wants to do anything special
            $_SESSION['session_id'] = self::$driver->regenerate();
        }

        // Get the session name
        $name = session_name();

        if (isset($_COOKIE[$name]))
        {
            // Change the cookie value to match the new session id to prevent "lag"
            $_COOKIE[$name] = $_SESSION['session_id'];
        }
    }

    /**
     * Destroys the current session.
     *
     * @return  void
     */
    public function destroy()
    {
        if (session_id() !== '')
        {
            // Get the session name
            $name = session_name();

            // Destroy the session
            session_destroy();

            // Re-initialize the array
            $_SESSION = array();

            // Delete the session cookie
            cookie::delete($name);
        }
    }

    /**
     * Runs the system.session_write event, then calls session_write_close.
     *
     * @return  void
     */
    public function write_close()
    {
        static $run;

        if ($run === NULL)
        {
            $run = TRUE;

            // Run the events that depend on the session being open
            Event::run('system.session_write');

            // Expire flash keys
            $this->expire_flash();

            // Close the session
            session_write_close();
        }
    }

    /**
     * Set a session variable.
     *
     * @param   string|array  key, or array of values
     * @param   mixed         value (if keys is not an array)
     * @return  void
     */
    public function set($keys, $val = FALSE)
    {
        if (empty($keys))
            return FALSE;

        if ( ! is_array($keys))
        {
            $keys = array($keys => $val);
        }

        foreach ($keys as $key => $val)
        {
            if (isset(self::$protect[$key]))
                continue;

            // Set the key
            $_SESSION[$key] = $val;
        }
    }

    /**
     * Set a flash variable.
     *
     * @param   string|array  key, or array of values
     * @param   mixed         value (if keys is not an array)
     * @return  void
     */
    public function set_flash($keys, $val = FALSE)
    {
        if (empty($keys))
            return FALSE;

        if ( ! is_array($keys))
        {
            $keys = array($keys => $val);
        }

        foreach ($keys as $key => $val)
        {
            if ($key == FALSE)
                continue;

            self::$flash[$key] = 'new';
            self::set($key, $val);
        }
    }

    /**
     * Freshen one, multiple or all flash variables.
     *
     * @param   string  variable key(s)
     * @return  void
     */
    public function keep_flash($keys = NULL)
    {
        $keys = ($keys === NULL) ? array_keys(self::$flash) : func_get_args();

        foreach ($keys as $key)
        {
            if (isset(self::$flash[$key]))
            {
                self::$flash[$key] = 'new';
            }
        }
    }

    /**
     * Expires old flash data and removes it from the session.
     *
     * @return  void
     */
    public function expire_flash()
    {
        static $run;

        // Method can only be run once
        if ($run === TRUE)
            return;

        if ( ! empty(self::$flash))
        {
            foreach (self::$flash as $key => $state)
            {
                if ($state === 'old')
                {
                    // Flash has expired
                    unset(self::$flash[$key], $_SESSION[$key]);
                }
                else
                {
                    // Flash will expire
                    self::$flash[$key] = 'old';
                }
            }
        }

        // Method has been run
        $run = TRUE;
    }

    /**
     * Get a variable. Access to sub-arrays is supported with key.subkey.
     *
     * @param   string  variable key
     * @param   mixed   default value returned if variable does not exist
     * @return  mixed   Variable data if key specified, otherwise array containing all session data.
     */
    public function get($key = FALSE, $default = FALSE)
    {
        if (empty($key))
            return $_SESSION;

        $result = isset($_SESSION[$key]) ? $_SESSION[$key] : Kohana::key_string($_SESSION, $key);

        return ($result === NULL) ? $default : $result;
    }

    /**
     * Get a variable, and delete it.
     *
     * @param   string  variable key
     * @param   mixed   default value returned if variable does not exist
     * @return  mixed
     */
    public function get_once($key, $default = FALSE)
    {
        $return = self::get($key, $default);
        self::delete($key);

        return $return;
    }

    /**
     * Delete one or more variables.
     *
     * @param   string  variable key(s)
     * @return  void
     */
    public function delete($keys)
    {
        $args = func_get_args();

        foreach ($args as $key)
        {
            if (isset(self::$protect[$key]))
                continue;

            // Unset the key
            unset($_SESSION[$key]);
        }
    }

} // End Session Class