What is happening?
The tutorial you select is submitted the server checks the see if the table named tutorial has a value matching the tutorial you selected. If there is a match then the webpage displays the matchinig data, in this case the tutorial. Simutanelously the comments table is queried to gather the comments that match the corresponding tutorial using a foreign key. If the user is logged in then a form is displayed allowing the user to give feedback. If the user is not logged in he is directed to the log in page via a link. Once the user has register and loged in they can then post a comment.