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

Solution Overview
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For this project, you begin by implementing a MySQL database that enables you to store
articles between each use.You then build simple interfaces to enable saving of articles.
When you load the list of articles for viewing, you will load the headers of each article
into a tree_node PHP class. Each tree_node will contain an article’s headers and a
set of the replies to that article.
The replies will be stored in an array. Each reply will itself be a tree_node that can
contain an array of replies to that article, which are themselves tree_nodes, and so on.This
process continues until you reach the so-called leaf nodes of the tree, the nodes that do not
have any replies.You then have a tree structure that looks like the one in Figure 31.1.
Some terminology:The message that you are replying to can be called the parent node
of the current node. Any replies to the message can be called the children of the current
node. If you imagine that this tree structure is like a family tree, this terminology will be
easy to remember.
The first article in this tree structure—the one with no parent—is sometimes called
the root node.
Note
Calling the first article the root can be unintuitive because you usually draw the root node at the top of
diagrams, unlike the roots of real trees.
To build and display the tree structure for this project, you will write recursive functions.
(We discussed recursion in Chapter 5,“Reusing Code and Writing Functions.”)
We decided to use a class for this structure because it’s the easiest way to build a complex,
dynamically expanding data structure for this application. It also means you have
quite simple, elegant code to do something quite complex.
Solution Overview
To really understand this project, it’s probably a good idea to work through the code,
which we do in a moment.This application has less bulk than some of the others, but
the code is a bit more complex.
This application contains only three real pages. It has a main index page that shows all
the articles in the forum as links to the articles. From here, you can add a new article,
view a listed article, or change the way the articles are viewed by expanding and collapsing
branches of the tree. (More on this shortly.) From the article view page, you can post
a reply to that article or view the existing replies to that article.The new article page
enables you to enter a new post, either a reply to an existing message or a new, unrelated
message.
The system flow diagram is shown in Figure 31.2.