PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

742 Chapter 31 Building Web Forums
Deciding how to display these relationships requires some careful thought. For this
system, users should be able to view an individual message, a thread of conversation with
the relationships shown, or all the threads on the system.
Users must also be able to post new topics or replies.This is the easy part.
Solution Components
As we mentioned previously, the process of storing and retrieving the author and text of a
message is easy.The most difficult part of this application is finding a database structure
that will store the information you want and a way of navigating that structure efficiently.
The structure of articles in a discussion might look like the one shown in Figure 31.1.
Initial posting Reply 1
Reply 1 to Reply 1
Reply 2 to Reply 1
Reply 2
Reply 3
Reply 1 to Reply 3
Figure 31.1 An article in a threaded discussion might be the first article in a
new topic, but more commonly it is a response to another article.
In this diagram, you can see that the initial posting starts off a topic, with three replies.
Some of the replies have replies.These replies could also have replies, and so on.
Looking at the diagram gives you a clue as to how you can store and retrieve the
article data and the links between articles.This diagram shows a tree structure. If you’ve
done much programming, you’ll know that this is one of the staple data structures
used. In the diagram, there are nodes—or articles—and links—or relationships between
articles—just as in any tree structure. (If you are not familiar with trees as a data structure,
don’t worry; we cover the basics as we go.)
The tricks to getting this all to work are
n Finding a way to map this tree structure into storage—in this case, into a MySQL
database
n Finding a way to reconstruct the data as required