So let’s jump right into the project, starting with Example 20-1, rnfunctions.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. So 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
$appname. If you want to
change the name, here’s the place to do so.
The project uses six main functions:
Checks whether a table already exists and, if not, creates it.
Returns a value of 1 if a table already exists, otherwise 0.
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” if they have one.
All of these should be obvious in their action to you by now, with the possible exception ...