Let’s jump right into the project, starting with Example 21-1, functions.php, the include file of main functions. This file contains a little more than just the functions, though, because I have added the database login details here instead of using yet another separate file.
The first half-dozen lines of code define the host, database name,
username, and password of the database to use. It doesn’t matter what you
call the database, as long as it already exists (see Chapter 8 for how to create a new database). Also
make sure to correctly assign a MySQL username and password to
$dbpass. With correct values, the subsequent two
lines will open a connection to MySQL and select the database. The last of
the initial instructions sets the name of the social networking site by
assigning the value “Robin’s Nest” to the variable
$appname. If you want to change the name, here’s
the place to do so.
The project uses five main functions:
Checks whether a table already exists and, if not, creates it.
Issues a query to MySQL, outputting an error message if it fails.
Destroys a PHP session and clears its data to log users out.
Removes potentially malicious code or tags from user input.
Displays a user’s image and “about me” message, if he has one.
All of these should be obvious in their action to you by now, with
the possible exception of
showProfile, which looks for an image of the
name <user>.jpg (where ...