# Class yii\web\DbSession

Inheritance | yii\web\DbSession » yii\web\MultiFieldSession » yii\web\Session » yii\base\Component » yii\base\BaseObject
Implements | ArrayAccess, Countable, IteratorAggregate, yii\base\Configurable
Available since version | 2.0
Source Code | https://github.com/yiisoft/yii2/blob/master/framework/web/DbSession.php

DbSession extends yii\web\Session by using database as session data storage.

By default, DbSession stores session data in a DB table named 'session'. This table must be pre-created. The table name can be changed by setting $sessionTable.

The following example shows how you can configure the application to use DbSession: Add the following to your application config under `components`:

    'session' => [
        'class' => 'yii\web\DbSession',
        // 'db' => 'mydb',
        // 'sessionTable' => 'my_session',
    ]

DbSession extends yii\web\MultiFieldSession, thus it allows saving extra fields into the $sessionTable. Refer to yii\web\MultiFieldSession for more details.

## Public Properties

Hide inherited properties

Property | Type | Description | Defined By
--- | --- | --- | ---
$allFlashes | array | Flash messages (key => message or key => [message1, message2]). This property is read-only. | yii\web\Session
$behaviors | yii\base\Behavior[] | List of behaviors attached to this component. This property is read-only. | yii\base\Component
$cacheLimiter | string | Current cache limiter. This property is read-only. | yii\web\Session
$cookieParams | array | The session cookie parameters. This property is read-only. | yii\web\Session
$count | integer | The number of session variables. This property is read-only. | yii\web\Session
$db | yii\db\Connection|array|string | The DB connection object or the application component ID of the DB connection. | yii\web\DbSession
$flash | string | The key identifying the flash message. Note that flash messages and normal session variables share the same name space. If you have a normal session variable using the same name, its value will be overwritten by this method. This property is write-only. | yii\web\Session
$flashParam | string | The name of the session variable that stores the flash message data. | yii\web\Session
$gCProbability | float | The probability (percentage) that the GC (garbage collection) process is started on every session initialization. | yii\web\Session
$handler | SessionHandlerInterface|array | An object implementing the SessionHandlerInterface or a configuration array. | yii\web\Session
$hasSessionId | boolean | Whether the current request has sent the session ID. | yii\web\Session
$id | string | The current session ID. | yii\web\Session
$isActive | boolean | Whether the session has started. This property is read-only. | yii\web\Session
$iterator | yii\web\SessionIterator | An iterator for traversing the session variables. This property is read-only. | yii\web\Session
$name | string | The current session name. | yii\web\Session
$readCallback | callable | A callback that will be called during session data reading. | yii\web\MultiFieldSession
$savePath | string | The current session save path, defaults to '/tmp'. | yii\web\Session
$sessionTable | string | The name of the DB table that stores the session data. | yii\web\DbSession
$timeout | integer | The number of seconds after which data will be seen as 'garbage' and cleaned up. The default value is 1440 seconds (or the value of "session.gc_maxlifetime" set in php.ini). | yii\web\Session
$useCookies | boolean|null | The value indicating whether cookies should be used to store session IDs. | yii\web\Session
$useCustomStorage | boolean | Whether to use custom storage. This property is read-only. | yii\web\Session
$useStrictMode | boolean | Whether strict mode is enabled or not. This property is read-only. | yii\web\Session
$useTransparentSessionID | boolean | Whether transparent sid support is enabled or not, defaults to false. | yii\web\Session
$writeCallback | callable | A callback that will be called during session data writing. | yii\web\MultiFieldSession

## Protected Properties

Hide inherited properties

Property | Type | Description | Defined By
--- | --- | --- | ---
$_forceRegenerateId | string|null | Holds the session id in case useStrictMode is enabled and the session id needs to be regenerated | yii\web\Session
$_originalSessionModule | string|null | Holds the original session module (before a custom handler is registered) so that it can be restored when a Session component without custom handler is used after one that has. | yii\web\Session
$fields | array | Session fields to be written into session table columns | yii\web\DbSession

## Public Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
__call() | Calls the named method which is not a class method. | yii\base\Component
__clone() | This method is called after the object is created by cloning an existing one. | yii\base\Component
__construct() | Constructor. | yii\base\BaseObject
__get() | Returns the value of a component property. | yii\base\Component
__isset() | Checks if a property is set, i.e. defined and not null. | yii\base\Component
__set() | Sets the value of a component property. | yii\base\Component
__unset() | Sets a component property to be null. | yii\base\Component
addFlash() | Adds a flash message. | yii\web\Session
attachBehavior() | Attaches a behavior to this component. | yii\base\Component
attachBehaviors() | Attaches a list of behaviors to the component. | yii\base\Component
behaviors() | Returns a list of behaviors that this component should behave as. | yii\base\Component
canGetProperty() | Returns a value indicating whether a property can be read. | yii\base\Component
canSetProperty() | Returns a value indicating whether a property can be set. | yii\base\Component
className() | Returns the fully qualified name of this class. | yii\base\BaseObject
close() | Ends the current session and store session data. | yii\web\DbSession
closeSession() | Session close handler. | yii\web\Session
count() | Returns the number of items in the session. | yii\web\Session
destroy() | Frees all session variables and destroys all data registered to a session. | yii\web\Session
destroySession() | Session destroy handler. | yii\web\DbSession
detachBehavior() | Detaches a behavior from the component. | yii\base\Component
detachBehaviors() | Detaches all behaviors from the component. | yii\base\Component
ensureBehaviors() | Makes sure that the behaviors declared in behaviors() are attached to this component. | yii\base\Component
gcSession() | Session GC (garbage collection) handler. | yii\web\DbSession
get() | Returns the session variable value with the session variable name. | yii\web\Session
getAllFlashes() | Returns all flash messages. | yii\web\Session
getBehavior() | Returns the named behavior object. | yii\base\Component
getBehaviors() | Returns all behaviors attached to this component. | yii\base\Component
getCacheLimiter() | Returns current cache limiter | yii\web\Session
getCookieParams() |  | yii\web\Session
getCount() | Returns the number of items in the session. | yii\web\Session
getFlash() | Returns a flash message. | yii\web\Session
getGCProbability() |  | yii\web\Session
getHasSessionId() | Returns a value indicating whether the current request has sent the session ID. | yii\web\Session
getId() | Gets the session ID. | yii\web\Session
getIsActive() |  | yii\web\Session
getIterator() | Returns an iterator for traversing the session variables. | yii\web\Session
getName() | Gets the name of the current session. | yii\web\Session
getSavePath() | Gets the current session save path. | yii\web\Session
getTimeout() |  | yii\web\Session
getUseCookies() | Returns the value indicating whether cookies should be used to store session IDs. | yii\web\Session
getUseCustomStorage() | Returns a value indicating whether to use custom session storage. | yii\web\Session
getUseStrictMode() |  | yii\web\Session
getUseTransparentSessionID() |  | yii\web\Session
has() |  | yii\web\Session
hasEventHandlers() | Returns a value indicating whether there is any handler attached to the named event. | yii\base\Component
hasFlash() | Returns a value indicating whether there are flash messages associated with the specified key. | yii\web\Session
hasMethod() | Returns a value indicating whether a method is defined. | yii\base\Component
hasProperty() | Returns a value indicating whether a property is defined for this component. | yii\base\Component
init() | Initializes the DbSession component. | yii\web\DbSession
off() | Detaches an existing event handler from this component. | yii\base\Component
offsetExists() | This method is required by the interface ArrayAccess. | yii\web\Session
offsetGet() | This method is required by the interface ArrayAccess. | yii\web\Session
offsetSet() | This method is required by the interface ArrayAccess. | yii\web\Session
offsetUnset() | This method is required by the interface ArrayAccess. | yii\web\Session
on() | Attaches an event handler to an event. | yii\base\Component
open() | Starts the session. | yii\web\Session
openSession() | Session open handler. | yii\web\DbSession
readSession() | Session read handler. | yii\web\DbSession
regenerateID() | Updates the current session ID with a newly generated one. | yii\web\DbSession
remove() | Removes a session variable. | yii\web\Session
removeAll() | Removes all session variables. | yii\web\Session
removeAllFlashes() | Removes all flash messages. | yii\web\Session
removeFlash() | Removes a flash message. | yii\web\Session
set() | Adds a session variable. | yii\web\Session
setCacheLimiter() | Set cache limiter | yii\web\Session
setCookieParams() | Sets the session cookie parameters. | yii\web\Session
setFlash() | Sets a flash message. | yii\web\Session
setGCProbability() |  | yii\web\Session
setHasSessionId() | Sets the value indicating whether the current request has sent the session ID. | yii\web\Session
setId() | Sets the session ID. | yii\web\Session
setName() | Sets the name for the current session. | yii\web\Session
setSavePath() | Sets the current session save path. | yii\web\Session
setTimeout() |  | yii\web\Session
setUseCookies() | Sets the value indicating whether cookies should be used to store session IDs. | yii\web\Session
setUseStrictMode() |  | yii\web\Session
setUseTransparentSessionID() |  | yii\web\Session
trigger() | Triggers an event. | yii\base\Component
writeSession() | Session write handler. | yii\web\DbSession

## Protected Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
composeFields() | Composes storage field set for session writing. | yii\web\MultiFieldSession
extractData() | Extracts session data from storage field set. | yii\web\MultiFieldSession
freeze() | If session is started it's not possible to edit session ini settings. In PHP7.2+ it throws exception. | yii\web\Session
getReadQuery() | Generates a query to get the session from db | yii\web\DbSession
registerSessionHandler() | Registers session handler. | yii\web\Session
typecastFields() | Method typecasts $fields before passing them to PDO. | yii\web\DbSession
unfreeze() | Starts session and restores data from temporary variable | yii\web\Session
updateFlashCounters() | Updates the counters for flash messages and removes outdated flash messages. | yii\web\Session

## Property Details

$db public property

The DB connection object or the application component ID of the DB connection. After the DbSession object is created, if you want to change this property, you should only assign it with a DB connection object. Starting from version 2.0.2, this can also be a configuration array for creating the object.

public yii\db\Connection|array|string $db = 'db'
$fields protected property (available since version 2.0.17)

Session fields to be written into session table columns

protected array $fields = []
$sessionTable public property

The name of the DB table that stores the session data. The table should be pre-created as follows:

    CREATE TABLE session
    (
        id CHAR(40) NOT NULL PRIMARY KEY,
        expire INTEGER,
        data BLOB
    )

where 'BLOB' refers to the BLOB-type of your preferred DBMS. Below are the BLOB type that can be used for some popular DBMS:

- MySQL: LONGBLOB
- PostgreSQL: BYTEA
- MSSQL: BLOB

When using DbSession in a production server, we recommend you create a DB index for the 'expire' column in the session table to improve the performance.

Note that according to the php.ini setting of `session.hash_function`, you may need to adjust the length of the `id` column. For example, if `session.hash_function=sha256`, you should use length 64 instead of 40.

public string $sessionTable = '{{%session}}'

## Method Details

close() public method (available since version 2.0.17)

Ends the current session and store session data.

public void close ( )

destroySession() public method

Session destroy handler.

public boolean destroySession ( $id )
$id | string | Session ID
return | boolean | Whether session is destroyed successfully

gcSession() public method

Session GC (garbage collection) handler.

public boolean gcSession ( $maxLifetime )
$maxLifetime | integer | The number of seconds after which data will be seen as 'garbage' and cleaned up.
return | boolean | Whether session is GCed successfully

getReadQuery() protected method

Generates a query to get the session from db

protected yii\db\Query getReadQuery ( $id )
$id | string | The id of the session

init() public method

Initializes the DbSession component.

This method will initialize the $db property to make sure it refers to a valid DB connection.

public void init ( )
throws | yii\base\InvalidConfigException | if $db is invalid.

openSession() public method

Session open handler.

public boolean openSession ( $savePath, $sessionName )
$savePath | string | Session save path
$sessionName | string | Session name
return | boolean | Whether session is opened successfully

readSession() public method

Session read handler.

public string readSession ( $id )
$id | string | Session ID
return | string | The session data

regenerateID() public method

Updates the current session ID with a newly generated one.

Please refer to https://secure.php.net/session_regenerate_id for more details.

This method has no effect when session is not active. Make sure to call open() before calling it.

public void regenerateID ( $deleteOldSession = false )
$deleteOldSession | boolean | Whether to delete the old associated session file or not.

typecastFields() protected method (available since version 2.0.13)

Method typecasts $fields before passing them to PDO.

Default implementation casts field `data` to `\PDO::PARAM_LOB`. You can override this method in case you need special type casting.

protected array typecastFields ( $fields )
$fields | array | Fields, that will be passed to PDO. Key - name, Value - value

writeSession() public method

Session write handler.

public boolean writeSession ( $id, $data )
$id | string | Session ID
$data | string | Session data
return | boolean | Whether session write is successful