This code checks if the user is authenticated by verifying the session variable 'authenticated'. If the variable is not set or is not true, the user is redirected to the login page. Package library: PHP has several packages and libraries that can be used for user authorisation, such as: - Laravel authentication library - Symfony Security Component - Yii Security Extension - CakePHP Authentication Plugin These packages provide pre-built components and functionalities for implementing user authentication and authorisation in PHP applications.