Sessions are used to store user-specific data that can be accessed across multiple pages.

For example, when a user logs in, we use sessions to remember their login status, username, or preferences until they log out or the session expires.

CodeIgniter provides a Session Library to handle this easily.

🔹 Step 1: Load the Session Library

CodeIgniter automatically loads the session library if enabled in autoload.php.

Open application/config/autoload.php:

$autoload['libraries'] = array('session');

If not autoloaded, you can load it in your controller:

$this->load->library('session');

🔹 Step 2: Storing Session Data

You can store session data as an array:

// Set session data
$userdata = array(
    'username'  => 'JohnDoe',
    'email'     => 'john@example.com',
    'logged_in' => TRUE
);
$this->session->set_userdata($userdata);

🔹 Step 3: Retrieving Session Data

// Get single data
$username = $this->session->userdata('username');

// Get all session data
print_r($this->session->all_userdata());

🔹 Step 4: Updating Session Data

$this->session->set_userdata('username', 'NewName');

🔹 Step 5: Removing Session Data

// Remove specific item
$this->session->unset_userdata('email');

// Destroy all sessions
$this->session->sess_destroy();

🔹 Step 6: Flashdata (Temporary Session Data)

Flashdata is session data that only lasts for the next request, usually for messages like success/error alerts.

// Set flashdata
$this->session->set_flashdata('success', 'User registered successfully!');

// Get flashdata
echo $this->session->flashdata('success');

🔹 Step 7: Tempdata (Session with Expiry Time)

You can also store data that expires after a specific time:

// Set tempdata (expires in 5 seconds)
$this->session->set_tempdata('promo', 'Discount applied!', 5);

// Get tempdata
echo $this->session->tempdata('promo');

🔹 Step 8: Session Configuration

Session settings are defined in application/config/config.php:

$config['sess_driver'] = 'files';   // or 'database'
$config['sess_cookie_name'] = 'ci_session';
$config['sess_expiration'] = 7200;  // 2 hours
$config['sess_save_path'] = sys_get_temp_dir(); // for file driver