This PHP code represents a secured web application with a data registration feature. The application consists of two main pages: a login page and a data registration page. The login page accepts a username and password, sanitizes the input, and stores the sanitized values in a PHP session. If the login button is clicked, a php file is included for authentication. The data registration page is accessible only to logged-in users. It contains a form where users can input their first name, last name, email, and phone number. Additionally, the form allows users to delete and update data based on a Data ID, create a database, add a table, and show the stored data. The corresponding PHP files are included to handle these operations. The page also includes header and footer files for consistent styling across the application. The application uses the W3.CSS framework, Bootstrap, Font Awesome icons, jQuery for styling and functionality.