/classes/Session.php

<?php

/**
 * Session Handling for PICKLES
 *
 * PHP version 5
 *
 * Licensed under The MIT License
 * Redistribution of these files must retain the above copyright notice.
 *
 * @author    Josh Sherman <josh@gravityblvd.com>
 * @copyright Copyright 2007-2011, Josh Sherman
 * @license   http://www.opensource.org/licenses/mit-license.html
 * @package   PICKLES
 * @link      http://p.ickl.es
 */

/**
 * Session Class
 *
 * Provides session handling via database instead of the file based session
 * handling built into PHP. Using this class requires an array to be defined
 * in place of the boolean true/false (on/off). If simply array(), the
 * datasource will default to the value in $config['pickles']['datasource'] and
 * if the table will default to "sessions". The format is as follows:
 *
 *     $config = array(
 *         'pickles' => array(
 *             'session' => array(
 *                 'datasource' => 'mysql',
 *                 'table'      => 'sessions',
 *             )
 *         )
 *     );
 *
 * In addition to the configuration variables, a table in your database must
 * be created. The [MySQL] table schema is as follows:
 *
 *     CREATE TABLE sessions (
 *         id varchar(32) COLLATE utf8_unicode_ci NOT NULL,
 *         session text COLLATE utf8_unicode_ci NOT NULL,
 *         expires_at datetime NOT NULL,
 *         PRIMARY KEY (id)
 *     ) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
 *
 * Note: The reason for not using a model class was to avoid a naming conflict
 * between the Session model and the Session class itself. This will eventually
 * be resolved when I abandon full 5.x support and migrate to 5.3+ (assuming
 * that ever happens).
 */
class Session extends Object
{
	/**
	 * Handler
	 *
	 * What the session is being handled by.
	 *
	 * @access private
	 * @var    string
	 */
	private $handler = false;

	/**
	 * Accessed At
	 *
	 * The UNIX timestamp of when the page was accessed.
	 *
	 * @access private
	 * @var    integer
	 */
	private $accessed_at = null;

	/**
	 * Time to Live
	 *
	 * The number of seconds the session should remain active. Corresponds to
	 * the INI variable session.gc_maxlifetime
	 *
	 * @access private
	 * @var    integer
	 */
	private $time_to_live = null;

	/**
	 * Datasource
	 *
	 * Name of the datasource, defaults to whatever the default datasource
	 * is defined to in config.php
	 *
	 * @access private
	 * @var    string
	 */
	private $datasource = null;

	/**
	 * Table
	 *
	 * Name of the database table in the aforementioned datasource that holds
	 * the session data. The expected schema is defined above.
	 *
	 * @access private
	 * @var    string
	 */
	private $table = null;

	/**
	 * Database
	 *
	 * Our database object to interact with the aforementioned datasource and
	 * table. This object is shared with other PICKLES internals.
	 *
	 * @access private
	 * @var    object
	 */
	private $db = null;

	/**
	 * Constructor
	 *
	 * All of our set up logic for the session in contained here. This object
	 * is initially instantiated from pickles.php and the session callbacks are
	 * established here. All variables are driven from php.ini and/or the site
	 * config. Once configured, the session is started automatically.
	 */
	public function __construct()
	{
		if (!IS_CLI && (isset($_REQUEST['request']) == false || preg_match('/^__pickles\/(css|js)\/.+$/', $_REQUEST['request']) == false))
		{
			parent::__construct();

			// Sets up our configuration variables
			$session     = $this->config->pickles['session'];
			$datasources = $this->config->datasources;

			$datasource = false;
			$table      = 'sessions';

			if (is_array($session))
			{
				if (isset($session['handler']) && in_array($session['handler'], array('files', 'memcache', 'mysql')))
				{
					$this->handler = $session['handler'];

					if ($this->handler != 'files')
					{
						if (isset($session['datasource']))
						{
							$datasource = $session['datasource'];
						}

						if (isset($session['table']))
						{
							$table = $session['table'];
						}
					}
				}
			}
			else
			{
				if ($session === true || $session == 'files')
				{
					$this->handler = 'files';
				}
				elseif ($session == 'memcache')
				{
					$this->handler = 'memcache';
					$datasource    = 'memcached';
				}
				elseif ($session == 'mysql')
				{
					$this->handler = 'mysql';
					$datasource    = 'mysql';
				}
			}

			switch ($this->handler)
			{
				case 'files':
					ini_set('session.save_handler', 'files');
					session_start();
					break;

				case 'memcache':
					$hostname = 'localhost';
					$port     = 11211;

					if ($datasource !== false && isset($datasources[$datasource]))
					{
						$hostname = $datasources[$datasource]['hostname'];
						$port     = $datasources[$datasource]['port'];
					}

					ini_set('session.save_handler', 'memcache');
					ini_set('session.save_path',    'tcp://' . $hostname . ':' . $port . '?persistent=1&amp;weight=1&amp;timeout=1&amp;retry_interval=15');
					session_start();
					break;

				case 'mysql':
					if ($datasource !== false && isset($datasources[$datasource]))
					{
						// Sets our access time and time to live
						$this->accessed_at  = time();
						$this->time_to_live = ini_get('session.gc_maxlifetime');

						$this->datasource = $datasource;
						$this->table      = $table;

						// Gets a database instance
						$this->db = Database::getInstance($this->datasource);

						// Initializes the session
						$this->initialize();

						session_start();
					}
					else
					{
						throw new Exception('Unable to determine which datasource to use');
					}

					break;
			}
		}
	}

	/**
	 * Destructor
	 *
	 * Runs garbage collection and closes the session. I'm not sure if the
	 * garbage collection should stay as it could be accomplished via php.ini
	 * variables. The session_write_close() is present to combat a chicken
	 * and egg scenario in earlier versions of PHP 5.
	 */
	public function __destruct()
	{
		if ($this->handler == 'mysql')
		{
			$this->gc($this->time_to_live);
			session_write_close();
		}
	}

	/**
	 * Initializes the Session
	 *
	 * This method exists to combat the fact that calling session_destroy()
	 * also clears out the save handler. Upon destorying a session this method
	 * is called again so the save handler is all set.
	 */
	public function initialize()
	{
		// Sets up the session handler
		session_set_save_handler(
			array($this, 'open'),
			array($this, 'close'),
			array($this, 'read'),
			array($this, 'write'),
			array($this, 'destroy'),
			array($this, 'gc')
		);

		register_shutdown_function('session_write_close');
	}

	/**
	 * Opens the Session
	 *
	 * Since the session is in the database, opens the database connection.
	 * This step isn't really necessary as the Database object is smart enough
	 * to open itself up upon execute.
	 */
	public function open()
	{
		session_regenerate_id();

		return $this->db->open();
	}

	/**
	 * Closes the Session
	 *
	 * Same as above, but in reverse.
	 */
	public function close()
	{
		return $this->db->close();
	}

	/**
	 * Reads the Session
	 *
	 * Checks the database for the session ID and returns the session data.
	 *
	 * @param  string $id session ID
	 * @return string serialized session data
	 */
	public function read($id)
	{
		$sql = 'SELECT session FROM `' . $this->table . '` WHERE id = ?;';

		$session = $this->db->fetch($sql, array($id));

		return isset($session[0]['session']) ? $session[0]['session'] : '';
	}

	/**
	 * Writes the Session
	 *
	 * When there's changes to the session, writes the data to the database.
	 *
	 * @param  string $id session ID
	 * @param  string $session serialized session data
	 * @return boolean whether the query executed correctly
	 */
	public function write($id, $session)
	{
		$sql = 'REPLACE INTO `' . $this->table . '` VALUES (?, ? ,?);';

		$parameters = array($id, $session, date('Y-m-d H:i:s', strtotime('+' . $this->time_to_live . ' seconds')));

		return $this->db->execute($sql, $parameters);
	}

	/**
	 * Destroys the Session
	 *
	 * Deletes the session from the database.
	 *
	 * @param  string $id session ID
	 * @return boolean whether the query executed correctly
	 */
	public function destroy($id)
	{
		$sql = 'DELETE FROM `' . $this->table . '` WHERE id = ?;';

		return $this->db->execute($sql, array($id));
	}

	/**
	 * Garbage Collector
	 *
	 * This is who you call when you got trash to be taken out.
	 *
	 * @param  integer $time_to_live number of seconds a session is active
	 * @return boolean whether the query executed correctly
	 */
	public function gc($time_to_live)
	{
		$sql = 'DELETE FROM `' . $this->table . '` WHERE expires_at < ?;';

		$parameters = array(date('Y-m-d H:i:s', $this->accessed_at - $time_to_live));

		return $this->db->execute($sql, $parameters);
	}
}

?>