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lnkohana/system/guide/kohana/sessions.md
2013-04-22 14:09:50 +10:00

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# Sessions
Kohana provides classes that make it easy to work with both cookies and sessions. At a high level both sessions and cookies provide the same functionality. They allow the developer to store temporary or persistent information about a specific client for later retrieval, usually to make something persistent between requests.
Sessions should be used for storing temporary or private data. Very sensitive data should be stored using the [Session] class with the "database" or "native" adapters. When using the "cookie" adapter, the session should always be encrypted.
[!!] For more information on best practices with session variables see [the seven deadly sins of sessions](http://lists.nyphp.org/pipermail/talk/2006-December/020358.html).
## Storing, Retrieving, and Deleting Data
[Cookie] and [Session] provide a very similar API for storing data. The main difference between them is that sessions are accessed using an object, and cookies are accessed using a static class.
Accessing the session instance is done using the [Session::instance] method:
// Get the session instance
$session = Session::instance();
When using sessions, you can also get all of the current session data using the [Session::as_array] method:
// Get all of the session data as an array
$data = $session->as_array();
You can also use this to overload the `$_SESSION` global to get and set data in a way more similar to standard PHP:
// Overload $_SESSION with the session data
$_SESSION =& $session->as_array();
// Set session data
$_SESSION[$key] = $value;
### Storing Data
Storing session or cookie data is done using the `set` method:
// Set session data
$session->set($key, $value);
// Or
Session::instance()->set($key, $value);
// Store a user id
$session->set('user_id', 10);
### Retrieving Data
Getting session or cookie data is done using the `get` method:
// Get session data
$data = $session->get($key, $default_value);
// Get the user id
$user = $session->get('user_id');
### Deleting Data
Deleting session or cookie data is done using the `delete` method:
// Delete session data
$session->delete($key);
// Delete the user id
$session->delete('user_id');
## Session Configuration
Always check these settings before making your application live, as many of them will have a direct affect on the security of your application.
## Session Adapters
When creating or accessing an instance of the [Session] class you can decide which session adapter or driver you wish to use. The session adapters that are available to you are:
Native
: Stores session data in the default location for your web server. The storage location is defined by [session.save_path](http://php.net/manual/session.configuration.php#ini.session.save-path) in `php.ini` or defined by [ini_set](http://php.net/ini_set).
Database
: Stores session data in a database table using the [Session_Database] class. Requires the [Database] module to be enabled.
Cookie
: Stores session data in a cookie using the [Cookie] class. **Sessions will have a 4KB limit when using this adapter, and should be encrypted.**
The default adapter can be set by changing the value of [Session::$default]. The default adapter is "native".
To access a Session using the default adapter, simply call [Session::instance()]. To access a Session using something other than the default, pass the adapter name to `instance()`, for example: `Session::instance('cookie')`
### Session Adapter Settings
You can apply configuration settings to each of the session adapters by creating a session config file at `APPPATH/config/session.php`. The following sample configuration file defines all the settings for each adapter:
[!!] As with cookies, a "lifetime" setting of "0" means that the session will expire when the browser is closed.
return array(
'native' => array(
'name' => 'session_name',
'lifetime' => 43200,
),
'cookie' => array(
'name' => 'cookie_name',
'encrypted' => TRUE,
'lifetime' => 43200,
),
'database' => array(
'name' => 'cookie_name',
'encrypted' => TRUE,
'lifetime' => 43200,
'group' => 'default',
'table' => 'table_name',
'columns' => array(
'session_id' => 'session_id',
'last_active' => 'last_active',
'contents' => 'contents'
),
'gc' => 500,
),
);
#### Native Adapter
Type | Setting | Description | Default
----------|-----------|---------------------------------------------------|-----------
`string` | name | name of the session | `"session"`
`integer` | lifetime | number of seconds the session should live for | `0`
#### Cookie Adapter
Type | Setting | Description | Default
----------|-----------|---------------------------------------------------|-----------
`string` | name | name of the cookie used to store the session data | `"session"`
`boolean` | encrypted | encrypt the session data using [Encrypt]? | `FALSE`
`integer` | lifetime | number of seconds the session should live for | `0`
#### Database Adapter
Type | Setting | Description | Default
----------|-----------|---------------------------------------------------|-----------
`string` | group | [Database::instance] group name | `"default"`
`string` | table | table name to store sessions in | `"sessions"`
`array` | columns | associative array of column aliases | `array`
`integer` | gc | 1:x chance that garbage collection will be run | `500`
`string` | name | name of the cookie used to store the session data | `"session"`
`boolean` | encrypted | encrypt the session data using [Encrypt]? | `FALSE`
`integer` | lifetime | number of seconds the session should live for | `0`
##### Table Schema
You will need to create the session storage table in the database. This is the default schema:
CREATE TABLE `sessions` (
`session_id` VARCHAR(24) NOT NULL,
`last_active` INT UNSIGNED NOT NULL,
`contents` TEXT NOT NULL,
PRIMARY KEY (`session_id`),
INDEX (`last_active`)
) ENGINE = MYISAM;
##### Table Columns
You can change the column names to match an existing database schema when connecting to a legacy session table. The default value is the same as the key value.
session_id
: the name of the "id" column
last_active
: UNIX timestamp of the last time the session was updated
contents
: session data stored as a serialized string, and optionally encrypted