How to save CakePHP session in Database ?
To store session in Database, you need to create a table in DB so that you can store the session in it.
Follow below steps.

1. Create a table in DB

CREATE TABLE IF NOT EXISTS `users` (
`id` VARCHAR(255) NOT NULL ,  // id column store the session id,
`data` TEXT NULL ,
`expires` INT UNSIGNED NULL ,
PRIMARY KEY (`id`) )

2. Go to the app/Config/core.php and search the following code.

Configure::write('Session', array(
            'defaults' => 'php'
        )); 

Replace above code to following code so that our application can store the session in database.

 Configure::write('Session', array(
    'defaults' => 'database',
    'handler' => array(
        'model' => 'User'
    )
));

3. Now create a file user.php in model folder and write following code.

class User extends AppModel
    {
      public function beforeSave($options = array()){}
   }