Session Management
Session Management¶
The Symfony HttpFoundation component has a very powerful and flexible session subsystem which is designed to provide session management through a simple object-oriented interface using a variety of session storage drivers.
Sessions are used via the simple Session
implementation of SessionInterface
interface.
Caution
Make sure your PHP session isn't already started before using the Session class. If you have a legacy session system that starts your session, see Legacy Sessions.
Quick example:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | use Symfony\Component\HttpFoundation\Session\Session;
$session = new Session();
$session->start();
// set and get session attributes
$session->set('name', 'Drak');
$session->get('name');
// set flash messages
$session->getFlashBag()->add('notice', 'Profile updated');
// retrieve messages
foreach ($session->getFlashBag()->get('notice', array()) as $message) {
echo '<div class="flash-notice">'.$message.'</div>';
}
|
Note
Symfony sessions are designed to replace several native PHP functions.
Applications should avoid using session_start()
, session_regenerate_id()
,
session_id()
, session_name()
, and session_destroy()
and instead
use the APIs in the following section.
Note
While it is recommended to explicitly start a session, a sessions will actually start on demand, that is, if any session request is made to read/write session data.
Caution
Symfony sessions are incompatible with php.ini
directive session.auto_start = 1
This directive should be turned off in php.ini
, in the webserver directives or
in .htaccess
.
Session API¶
The Session
class implements
SessionInterface
.
The Session
has a simple API
as follows divided into a couple of groups.
Session workflow
start()
: Starts the session - do not usesession_start()
;migrate()
: Regenerates the session ID - do not usesession_regenerate_id()
. This method can optionally change the lifetime of the new cookie that will be emitted by calling this method;invalidate()
: Clears all session data and regenerates session ID. Do not usesession_destroy()
;getId()
: Gets the session ID. Do not usesession_id()
;setId()
: Sets the session ID. Do not usesession_id()
;getName()
: Gets the session name. Do not usesession_name()
;setName()
: Sets the session name. Do not usesession_name()
.
Session attributes
set()
: Sets an attribute by key;get()
: Gets an attribute by key;all()
: Gets all attributes as an array of key => value;has()
: Returns true if the attribute exists;replace()
: Sets multiple attributes at once: takes a keyed array and sets each key => value pair;remove()
: Deletes an attribute by key;clear()
: Clear all attributes.
The attributes are stored internally in a "Bag", a PHP object that acts like an array. A few methods exist for "Bag" management:
registerBag()
: Registers aSessionBagInterface
;getBag()
: Gets aSessionBagInterface
by bag name;getFlashBag()
: Gets theFlashBagInterface
. This is just a shortcut for convenience.
Session metadata
getMetadataBag()
: Gets theMetadataBag
which contains information about the session.
Session Data Management¶
PHP's session management requires the use of the $_SESSION
super-global,
however, this interferes somewhat with code testability and encapsulation in an
OOP paradigm. To help overcome this, Symfony uses session bags linked to the
session to encapsulate a specific dataset of attributes or flash messages.
This approach also mitigates namespace pollution within the $_SESSION
super-global because each bag stores all its data under a unique namespace.
This allows Symfony to peacefully co-exist with other applications or libraries
that might use the $_SESSION
super-global and all data remains completely
compatible with Symfony's session management.
Symfony provides two kinds of storage bags, with two separate implementations. Everything is written against interfaces so you may extend or create your own bag types if necessary.
SessionBagInterface
has
the following API which is intended mainly for internal purposes:
getStorageKey()
: Returns the key which the bag will ultimately store its array under in$_SESSION
. Generally this value can be left at its default and is for internal use.initialize()
: This is called internally by Symfony session storage classes to link bag data to the session.getName()
: Returns the name of the session bag.
Attributes¶
The purpose of the bags implementing the AttributeBagInterface
is to handle session attribute storage. This might include things like user ID,
and remember me login settings or other user based state information.
AttributeBag
This is the standard default implementation.NamespacedAttributeBag
This implementation allows for attributes to be stored in a structured namespace.
Any plain key-value storage system is limited in the extent to which
complex data can be stored since each key must be unique. You can achieve
namespacing by introducing a naming convention to the keys so different parts of
your application could operate without clashing. For example, module1.foo
and
module2.foo
. However, sometimes this is not very practical when the attributes
data is an array, for example a set of tokens. In this case, managing the array
becomes a burden because you have to retrieve the array then process it and
store it again:
1 2 | $tokens = array('tokens' => array('a' => 'a6c1e0b6',
'b' => 'f4a7b1f3'));
|
So any processing of this might quickly get ugly, even simply adding a token to the array:
1 2 3 | $tokens = $session->get('tokens');
$tokens['c'] = $value;
$session->set('tokens', $tokens);
|
With structured namespacing, the key can be translated to the array structure like this using a namespace character (defaults to /):
1 | $session->set('tokens/c', $value);
|
This way you can easily access a key within the stored array directly and easily.
AttributeBagInterface
has a simple API
set()
: Sets an attribute by key;get()
: Gets an attribute by key;all()
: Gets all attributes as an array of key => value;has()
: Returns true if the attribute exists;keys()
: Returns an array of stored attribute keys;replace()
: Sets multiple attributes at once: takes a keyed array and sets each key => value pair.remove()
: Deletes an attribute by key;clear()
: Clear the bag;
Flash Messages¶
The purpose of the FlashBagInterface
is to provide a way of setting and retrieving messages on a per session basis.
The usual workflow would be to set flash messages in a request and to display them
after a page redirect. For example, a user submits a form which hits an update
controller, and after processing the controller redirects the page to either the
updated page or an error page. Flash messages set in the previous page request
would be displayed immediately on the subsequent page load for that session.
This is however just one application for flash messages.
AutoExpireFlashBag
In this implementation, messages set in one page-load will be available for display only on the next page load. These messages will auto expire regardless of if they are retrieved or not.
FlashBag
In this implementation, messages will remain in the session until they are explicitly retrieved or cleared. This makes it possible to use ESI caching.
FlashBagInterface
has a simple API
add()
: Adds a flash message to the stack of specified type;set()
: Sets flashes by type; This method conveniently takes both single messages as astring
or multiple messages in anarray
.get()
: Gets flashes by type and clears those flashes from the bag;setAll()
: Sets all flashes, accepts a keyed array of arraystype => array(messages)
;all()
: Gets all flashes (as a keyed array of arrays) and clears the flashes from the bag;peek()
: Gets flashes by type (read only);peekAll()
: Gets all flashes (read only) as keyed array of arrays;has()
: Returns true if the type exists, false if not;keys()
: Returns an array of the stored flash types;clear()
: Clears the bag;
For simple applications it is usually sufficient to have one flash message per
type, for example a confirmation notice after a form is submitted. However,
flash messages are stored in a keyed array by flash $type
which means your
application can issue multiple messages for a given type. This allows the API
to be used for more complex messaging in your application.
Examples of setting multiple flashes:
1 2 3 4 5 6 7 8 9 10 11 12 | use Symfony\Component\HttpFoundation\Session\Session;
$session = new Session();
$session->start();
// add flash messages
$session->getFlashBag()->add(
'warning',
'Your config file is writable, it should be set read-only'
);
$session->getFlashBag()->add('error', 'Failed to update name');
$session->getFlashBag()->add('error', 'Another error');
|
Displaying the flash messages might look as follows.
Simple, display one type of message:
1 2 3 4 5 6 7 8 9 | // display warnings
foreach ($session->getFlashBag()->get('warning', array()) as $message) {
echo '<div class="flash-warning">'.$message.'</div>';
}
// display errors
foreach ($session->getFlashBag()->get('error', array()) as $message) {
echo '<div class="flash-error">'.$message.'</div>';
}
|
Compact method to process display all flashes at once:
1 2 3 4 5 | foreach ($session->getFlashBag()->all() as $type => $messages) {
foreach ($messages as $message) {
echo '<div class="flash-'.$type.'">'.$message.'</div>';
}
}
|
This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.