Header php files are also being used to enable the connection to database and to make changes to certain sections easier e.g. Navigation Bar
Authentication functionality has been enabled. User must login to access pages beyond login.php
Please make note of naming conventions (for classes and names) used for consistency. This can be changed, though checks must be made to ensure that changes don't break the applications core functionality. Divs, classes, ids and other such elements can/should be added in order to help with the styling of the application. The HTML and PHP should be indented and follow conventions.