Session Library

The Session class permits you to maintain a user’s “state” and track their activity while they browse your site.

CodeIgniter comes with a few session storage drivers, that you can see in the last section of the table of contents:

Using the Session Class

Initializing a Session

Sessions will typically run globally with each page load, so the Session class should be magically initialized.

To access and initialize the session:

<?php

$session = service('session', $config);

The $config parameter is optional - your application configuration. If not provided, the services register will instantiate your default one.

Once loaded, the Sessions library object will be available using:

$session

Alternatively, you can use the helper function that will use the default configuration options. This version is a little friendlier to read, but does not take any configuration options.

<?php

$session = session();

How Do Sessions Work?

When a page is loaded, the session class will check to see if a valid session cookie is sent by the user’s browser. If a session cookie does not exist (or if it doesn’t match one stored on the server or has expired) a new session will be created and saved.

If a valid session does exist, its information will be updated. With each update, the session ID may be regenerated if configured to do so.

It’s important for you to understand that once initialized, the Session class runs automatically. There is nothing you need to do to cause the above behavior to happen. You can, as you’ll see below, work with session data, but the process of reading, writing, and updating a session is automatic.

Note

Under CLI, the Session library will automatically halt itself, as this is a concept based entirely on the HTTP protocol.

A Note about Concurrency

Unless you’re developing a website with heavy AJAX usage, you can skip this section. If you are, however, and if you’re experiencing performance issues, then this note is exactly what you’re looking for.

Sessions in CodeIgniter v2.x didn’t implement locking, which meant that two HTTP requests using the same session could run exactly at the same time. To use a more appropriate technical term - requests were non-blocking.

However, non-blocking requests in the context of sessions also means unsafe, because, modifications to session data (or session ID regeneration) in one request can interfere with the execution of a second, concurrent request. This detail was at the root of many issues and the main reason why CodeIgniter 3 has a completely re-written Session library.

Why are we telling you this? Because it is likely that after trying to find the reason for your performance issues, you may conclude that locking is the issue and therefore look into how to remove the locks …

DO NOT DO THAT! Removing locks would be wrong and it will cause you more problems!

Locking is not the issue, it is a solution. Your issue is that you still have the session open, while you’ve already processed it and therefore no longer need it. So, what you need is to close the session for the current request after you no longer need it.

<?php

$session->close();

What is Session Data?

Session data is simply an array associated with a particular session ID (cookie).

If you’ve used sessions in PHP before, you should be familiar with PHP’s $_SESSION superglobal (if not, please read the content on that link).

CodeIgniter gives access to its session data through the same means, as it uses the session handlers’ mechanism provided by PHP. Using session data is as simple as manipulating (read, set and unset values) the $_SESSION array.

Note

In general, it is bad practice to use global variables. So using the superglobal $_SESSION directly is not recommended.

In addition, CodeIgniter also provides 2 special types of session data that are further explained below: Flashdata and Tempdata.

Note

For historical reasons, we refer to session data excluding Flashdata and Tempdata as “userdata”.

Retrieving Session Data

Any piece of information from the session array is available through the $_SESSION superglobal:

<?php

$item = $_SESSION['item'];

Or through the conventional accessor method:

<?php

$item = $session->get('item');

Or through the magic getter:

<?php

$item = $session->item;

Or even through the session helper method:

<?php

$item = session('item');

Where item is the array key corresponding to the item you wish to fetch. For example, to assign a previously stored name item to the $name variable, you will do this:

<?php

$name = $_SESSION['name'];

// or:

$name = $session->name;

// or:

$name = $session->get('name');

Note

The get() method returns null if the item you are trying to access does not exist.

If you want to retrieve all of the existing session data, you can simply omit the item key (magic getter only works for single property values):

<?php

$userData = $_SESSION;
// or:
$userData = $session->get();

Important

The get() method WILL return flashdata or tempdata items when retrieving a single item by key. It will not return flashdata or tempdata when grabbing all data from the session, however.

Adding Session Data

Let’s say a particular user logs into your site. Once authenticated, you could add their username and e-mail address to the session, making that data globally available to you without having to run a database query when you need it.

You can simply assign data to the $_SESSION array, as with any other variable. Or as a property of $session.

You can pass an array containing your new session data to the set() method:

<?php

$session->set($array);

Where $array is an associative array containing your new data. Here’s an example:

<?php

$newdata = [
    'username'  => 'johndoe',
    'email'     => 'johndoe@some-site.com',
    'logged_in' => true,
];

$session->set($newdata);

If you want to add session data one value at a time, set() also supports this syntax:

<?php

$session->set('some_name', 'some_value');

If you want to verify that a session value exists, simply check with isset():

<?php

// returns false if the 'some_name' item doesn't exist or is null,
// true otherwise:
if (isset($_SESSION['some_name'])) {
    // ...
}

Or you can call has():

<?php

$session->has('some_name');

Pushing New Value to Session Data

The push() method is used to push a new value onto a session value that is an array. For instance, if the hobbies key contains an array of hobbies, you can add a new value onto the array like so:

<?php

$session->push('hobbies', ['sport' => 'tennis']);

Removing Session Data

Just as with any other variable, unsetting a value in $_SESSION can be done through unset():

<?php

unset($_SESSION['some_name']);
// or multiple values:
unset(
    $_SESSION['some_name'],
    $_SESSION['another_name']
);

Also, just as set() can be used to add information to a session, remove() can be used to remove it, by passing the session key. For example, if you wanted to remove some_name from your session data array:

<?php

$session->remove('some_name');

This method also accepts an array of item keys to unset:

<?php

$array_items = ['username', 'email'];
$session->remove($array_items);

Flashdata

CodeIgniter supports “flashdata”, or session data that will only be available for the next request, and is then automatically cleared.

This can be very useful, especially for one-time informational, error or status messages (for example: “Record 2 deleted”).

It should be noted that flashdata variables are regular session variables, managed inside the CodeIgniter session handler.

To mark an existing item as “flashdata”:

<?php

$session->markAsFlashdata('item');

If you want to mark multiple items as flashdata, simply pass the keys as an array:

<?php

$session->markAsFlashdata(['item', 'item2']);

To add flashdata:

<?php

$_SESSION['item'] = 'value';
$session->markAsFlashdata('item');

Or alternatively, using the setFlashdata() method:

<?php

$session->setFlashdata('item', 'value');

You can also pass an array to setFlashdata(), in the same manner as set().

Reading flashdata variables is the same as reading regular session data through $_SESSION:

<?php

$item = $_SESSION['item'];

Important

The get() method WILL return flashdata items when retrieving a single item by key. It will not return flashdata when grabbing all data from the session, however.

However, if you want to be sure that you’re reading “flashdata” (and not any other kind), you can also use the getFlashdata() method:

<?php

$session->getFlashdata('item');

Note

The getFlashdata() method returns null if the item cannot be found.

Or to get an array with all flashdata, simply omit the key parameter:

<?php

$session->getFlashdata();

If you find that you need to preserve a flashdata variable through an additional request, you can do so using the keepFlashdata() method. You can either pass a single item or an array of flashdata items to keep.

<?php

$session->keepFlashdata('item');
$session->keepFlashdata(['item1', 'item2', 'item3']);

Tempdata

CodeIgniter also supports “tempdata”, or session data with a specific expiration time. After the value expires, or the session expires or is deleted, the value is automatically removed.

Similarly to flashdata, tempdata variables are managed internally by the CodeIgniter session handler.

To mark an existing item as “tempdata”, simply pass its key and expiry time (in seconds!) to the markAsTempdata() method:

<?php

// 'item' will be erased after 300 seconds
$session->markAsTempdata('item', 300);

You can mark multiple items as tempdata in two ways, depending on whether you want them all to have the same expiry time or not:

<?php

// Both 'item' and 'item2' will expire after 300 seconds
$session->markAsTempdata(['item', 'item2'], 300);

// 'item' will be erased after 300 seconds, while 'item2'
// will do so after only 240 seconds
$session->markAsTempdata([
    'item'  => 300,
    'item2' => 240,
]);

To add tempdata:

<?php

$_SESSION['item'] = 'value';
$session->markAsTempdata('item', 300); // Expire in 5 minutes

Or alternatively, using the setTempdata() method:

<?php

$session->setTempdata('item', 'value', 300);

You can also pass an array to setTempdata():

<?php

$tempdata = ['newuser' => true, 'message' => 'Thanks for joining!'];
$session->setTempdata($tempdata, null, $expire);

Note

If the expiration is omitted or set to 0, the default time-to-live value of 300 seconds (or 5 minutes) will be used.

To read a tempdata variable, again you can just access it through the $_SESSION superglobal array:

<?php

$item = $_SESSION['item'];

Important

The get() method WILL return tempdata items when retrieving a single item by key. It will not return tempdata when grabbing all data from the session, however.

Or if you want to be sure that you’re reading “tempdata” (and not any other kind), you can also use the getTempdata() method:

<?php

$session->getTempdata('item');

Note

The getTempdata() method returns null if the item cannot be found.

And of course, if you want to retrieve all existing tempdata:

<?php

$session->getTempdata();

If you need to remove a tempdata value before it expires, you can directly unset it from the $_SESSION array:

<?php

unset($_SESSION['item']);

However, this won’t remove the marker that makes this specific item to be tempdata (it will be invalidated on the next HTTP request), so if you intend to reuse that same key in the same request, you’d want to use removeTempdata():

<?php

$session->removeTempdata('item');

Closing a Session

close()

New in version 4.4.0.

To close the current session manually after you no longer need it, use the close() method:

<?php

$session->close();

You do not have to close the session manually, PHP will close it automatically after your script terminated. But as session data is locked to prevent concurrent writes only one request may operate on a session at any time. You may improve your site performance by closing the session as soon as all changes to session data are done.

This method will work in exactly the same way as PHP’s session_write_close() function.

Destroying a Session

destroy()

To clear the current session (for example, during a logout), you may simply use the library’s destroy() method:

<?php

$session->destroy();

This method will work in exactly the same way as PHP’s session_destroy() function.

This must be the last session-related operation that you do during the same request. All session data (including flashdata and tempdata) will be destroyed permanently.

Note

You do not have to call this method from usual code. Cleanup session data rather than destroying the session.

stop()

Deprecated since version 4.3.5.

The session class also has the stop() method.

Warning

Prior to v4.3.5, this method did not destroy the session due to a bug.

Starting with v4.3.5, this method has been modified to destroy the session. However, it is deprecated because it is exactly the same as the destroy() method. Use the destroy() method instead.

Accessing Session Metadata

In CodeIgniter 2, the session data array included 4 items by default: ‘session_id’, ‘ip_address’, ‘user_agent’, ‘last_activity’.

This was due to the specifics of how sessions worked, but is now no longer necessary with our new implementation. However, it may happen that your application relied on these values, so here are alternative methods of accessing them:

• session_id: $session->session_id or session_id() (PHP’s built-in function)

• ip_address: $_SERVER['REMOTE_ADDR']

• user_agent: $_SERVER['HTTP_USER_AGENT'] (unused by sessions)

• last_activity: Depends on the storage, no straightforward way. Sorry!

Session Preferences

CodeIgniter will usually make everything work out of the box. However, Sessions are a very sensitive component of any application, so some careful configuration must be done. Please take your time to consider all of the options and their effects.

Note

Since v4.3.0, the new app/Config/Session.php has been added. Previously, the Session Preferences were in your app/Config/App.php file.

You’ll find the following Session related preferences in your app/Config/Session.php file:

Preference	Default	Options	Description
driver	CodeIgniter\Session\Handlers\FileHandler	CodeIgniter\Session\Handlers\FileHandler CodeIgniter\Session\Handlers\DatabaseHandler CodeIgniter\Session\Handlers\MemcachedHandler CodeIgniter\Session\Handlers\RedisHandler CodeIgniter\Session\Handlers\ArrayHandler	The session storage driver to use.
cookieName	ci_session	[A-Za-z_-] characters only	The name used for the session cookie.
expiration	7200 (2 hours)	Time in seconds (integer)	The number of seconds you would like the session to last. If you would like a non-expiring session (until browser is closed) set the value to zero: 0
savePath	null	None	Specifies the storage location, depends on the driver being used.
matchIP	false	true/false (boolean)	Whether to validate the user’s IP address when reading the session cookie. Note that some ISPs dynamically changes the IP, so if you want a non-expiring session you will likely set this to false.
timeToUpdate	300	Time in seconds (integer)	This option controls how often the session class will regenerate itself and create a new session ID. Setting it to 0 will disable session ID regeneration.
regenerateDestroy	false	true/false (boolean)	Whether to destroy session data associated with the old session ID when auto-regenerating the session ID. When set to false, the data will be later deleted by the garbage collector.

Note

As a last resort, the Session library will try to fetch PHP’s session related INI settings, as well as CodeIgniter 3 settings such as ‘sess_expire_on_close’ when any of the above is not configured. However, you should never rely on this behavior as it can cause unexpected results or be changed in the future. Please configure everything properly.

Note

If expiration is set to 0, the session.gc_maxlifetime setting set by PHP in session management will be used as-is (often the default value of 1440). This needs to be changed in php.ini or via ini_set() as needed.

In addition to the values above, the Session cookie uses the following configuration values in your app/Config/Cookie.php file:

Preference	Default	Description
domain	‘’	The domain for which the session is applicable
path	/	The path to which the session is applicable
secure	false	Whether to create the session cookie only on encrypted (HTTPS) connections
sameSite	Lax	The SameSite setting for the session cookie

Note

The httponly setting (in app/Config/Cookie.php) doesn’t have an effect on sessions. Instead the HttpOnly parameter is always enabled, for security reasons. Additionally, the Config\Cookie::$prefix setting is completely ignored.

Session Drivers

As already mentioned, the Session library comes with five handlers, or storage engines, that you can use:

• CodeIgniter\Session\Handlers\FileHandler

• CodeIgniter\Session\Handlers\DatabaseHandler

• CodeIgniter\Session\Handlers\MemcachedHandler

• CodeIgniter\Session\Handlers\RedisHandler

• CodeIgniter\Session\Handlers\ArrayHandler

By default, the FileHandler will be used when a session is initialized, because it is the safest choice and is expected to work everywhere (virtually every environment has a file system).

However, any other driver may be selected via the $driver setting in your app/Config/Session.php file, if you chose to do so. Have it in mind though, every driver has different caveats, so be sure to get yourself familiar with them (below) before you make that choice.

Note

The ArrayHandler is used during testing and stores all data within a PHP array, while preventing the data from being persisted.

FileHandler Driver (the default)

The ‘FileHandler’ driver uses your file system for storing session data.

It can safely be said that it works exactly like PHP’s own default session implementation, but in case this is an important detail for you, in fact it is not the same code and it has some limitations (and advantages).

To be more specific, it doesn’t support PHP’s directory level and mode formats used in session.save_path, and it has most of the options hard-coded for safety. Instead, only absolute paths are supported with $savePath setting.

Another important thing that you should know, is to make sure that you don’t use a publicly-readable or shared directory for storing your session files. Only you should have access to the contents of your chosen savePath directory. Otherwise, anybody can see and steal session data (also known as “session fixation” attack).

On UNIX-like operating systems, this is usually achieved by setting the 0700 mode permissions on that directory via the chmod command, which allows only the directory’s owner to perform read and write operations on it. But be careful because the system user running the script is usually not your own, but something like ‘www-data’ instead, so only setting those permissions will probably break your application.

Instead, you should do something like this, depending on your environment:

mkdir /<path to your application directory>/writable/sessions/
chmod 0700 /<path to your application directory>/writable/sessions/
chown www-data /<path to your application directory>/writable/sessions/

Bonus Tip

Some of you will probably opt to choose another session driver because file storage is usually slower. This is only half true.

A very basic test will probably trick you into believing that an SQL database is faster, but in 99% of the cases, this is true only if you have a few current sessions. As the sessions count and server loads increase - which is the time when it matters - the file system will consistently outperform almost all relational database setups.

In addition, if performance is your only concern, you may want to look into using tmpfs, which can make your sessions blazing fast.

DatabaseHandler Driver

Important

Only MySQL and PostgreSQL databases are officially supported, due to lack of advisory locking mechanisms on other platforms. Using sessions without locks can cause all sorts of problems, especially with heavy usage of AJAX. Use the close() method after you’ve done processing session data if you’re having performance issues.

The ‘DatabaseHandler’ driver uses a relational database such as MySQL or PostgreSQL to store sessions. This is a popular choice among many users, because it allows the developer easy access to the session data within an application - it is just another table in your database.

However, there is a restriction: You can NOT use a persistent connection.

Configure DatabaseHandler

Setting Table Name

In order to use the ‘DatabaseHandler’ session driver, you must also create this table that we already mentioned and then set it as your $savePath value. For example, if you would like to use ‘ci_sessions’ as your table name, you would do this:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;
use CodeIgniter\Session\Handlers\FileHandler;

class Session extends BaseConfig
{
    // ...
    public string $driver = 'CodeIgniter\Session\Handlers\DatabaseHandler';

    // ...
    public string $savePath = 'ci_sessions';

    // ...
}

Creating Database Table

And then of course, create the database table.

For MySQL:

CREATE TABLE IF NOT EXISTS `ci_sessions` (
    `id` varchar(128) NOT null,
    `ip_address` varchar(45) NOT null,
    `timestamp` timestamp DEFAULT CURRENT_TIMESTAMP NOT null,
    `data` blob NOT null,
    KEY `ci_sessions_timestamp` (`timestamp`)
);

For PostgreSQL:

CREATE TABLE "ci_sessions" (
    "id" varchar(128) NOT NULL,
    "ip_address" inet NOT NULL,
    "timestamp" timestamptz DEFAULT CURRENT_TIMESTAMP NOT NULL,
    "data" bytea DEFAULT '' NOT NULL
);

CREATE INDEX "ci_sessions_timestamp" ON "ci_sessions" ("timestamp");

Note

The id value contains the session cookie name (Config\Session::$cookieName) and the session ID and a delimiter. It should be increased as needed, for example, when using long session IDs.

Adding Primary Key

You will also need to add a PRIMARY KEY depending on your $matchIP setting. The examples below work both on MySQL and PostgreSQL:

// When $matchIP = true
ALTER TABLE ci_sessions ADD PRIMARY KEY (id, ip_address);

// When $matchIP = false
ALTER TABLE ci_sessions ADD PRIMARY KEY (id);

// To drop a previously created primary key (use when changing the setting)
ALTER TABLE ci_sessions DROP PRIMARY KEY;

Important

If you don’t add the correct primary key, the following error may occur:

Uncaught mysqli_sql_exception: Duplicate entry 'ci_session:***' for key 'ci_sessions.PRIMARY'

Changing Database Group

The default database group is used by default. You can change the database group to use by changing the $DBGroup property in the app/Config/Session.php file to the name of the group to use:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;
use CodeIgniter\Session\Handlers\FileHandler;

class Session extends BaseConfig
{
    // ...
    public ?string $DBGroup = 'groupName';
}

Setting Up Database Table with Command

If you’d rather not do all of this by hand, you can use the make:migration --session command from the cli to generate a migration file for you:

php spark make:migration --session
php spark migrate

This command will take the $savePath and $matchIP settings into account when it generates the code.

RedisHandler Driver

Note

Since Redis doesn’t have a locking mechanism exposed, locks for this driver are emulated by a separate value that is kept for up to 300 seconds.

Note

Starting with v4.3.2, you can connect Redis with TLS protocol.

Redis is a storage engine typically used for caching and popular because of its high performance, which is also probably your reason to use the ‘RedisHandler’ session driver.

The downside is that it is not as ubiquitous as relational databases and requires the phpredis PHP extension to be installed on your system, and that one doesn’t come bundled with PHP. Chances are, you’re using the RedisHandler driver only if you’re already both familiar with Redis and using it for other purposes.

Configure RedisHandler

Just as with the ‘FileHandler’ and ‘DatabaseHandler’ drivers, you must also configure the storage location for your sessions via the $savePath setting. The format here is a bit different and complicated. It is best explained by the phpredis extension’s README file, so we’ll simply give a link to it:

https://github.com/phpredis/phpredis

For the most common case however, a simple host:port pair should be sufficient:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;
use CodeIgniter\Session\Handlers\FileHandler;

class Session extends BaseConfig
{
    // ...
    public string $driver = 'CodeIgniter\Session\Handlers\RedisHandler';

    // ...
    public string $savePath = 'tcp://localhost:6379';

    // ...
}

Starting with v4.5.0, you can use Redis ACL (username and password):

public string $savePath = 'tcp://localhost:6379?auth[user]=username&auth[pass]=password';

Note

Starting with v4.5.0, the interval time for acquiring locks ($lockRetryInterval) and the number of retries ($lockMaxRetries) are configurable.

MemcachedHandler Driver

Note

Since Memcached doesn’t have a locking mechanism exposed, locks for this driver are emulated by a separate value that is kept for up to 300 seconds.

The ‘MemcachedHandler’ driver is very similar to the ‘RedisHandler’ one in all of its properties, except perhaps for availability, because PHP’s Memcached extension is distributed via PECL and some Linux distributions make it available as an easy to install package.

Other than that, and without any intentional bias towards Redis, there’s not much different to be said about Memcached - it is also a popular product that is usually used for caching and famed for its speed.

However, it is worth noting that the only guarantee given by Memcached is that setting value X to expire after Y seconds will result in it being deleted after Y seconds have passed (but not necessarily that it won’t expire earlier than that time). This happens very rarely, but should be considered as it may result in loss of sessions.

Configure MemcachedHandler

The $savePath format is fairly straightforward here, being just a host:port pair:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;
use CodeIgniter\Session\Handlers\FileHandler;

class Session extends BaseConfig
{
    // ...
    public string $driver = 'CodeIgniter\Session\Handlers\MemcachedHandler';

    // ...
    public string $savePath = 'localhost:11211';

    // ...
}

Bonus Tip

Multi-server configuration with an optional weight parameter as the third colon-separated (:weight) value is also supported, but we have to note that we haven’t tested if that is reliable.

If you want to experiment with this feature (on your own risk), simply separate the multiple server paths with commas:

<?php

namespace Config;

use CodeIgniter\Config\BaseConfig;
use CodeIgniter\Session\Handlers\FileHandler;

class Session extends BaseConfig
{
    // ...

    // localhost will be given higher priority (5) here,
    // compared to 192.0.2.1 with a weight of 1.
    public string $savePath = 'localhost:11211:5,192.0.2.1:11211:1';

    // ...
}