Learning PHP, MySQL, and JavaScript

Creating a Connect Instance

With all of PEAR, the MDB2 package, and the MySQL driver installed, you can start to take advantage of these new additions. But to do so, you need to understand what MDB2 is providing you with: a layer of abstraction.

In other words, MDB2 knows everything about accessing any major brand of database program you may have installed. You simply use a common set of commands and tell MDB2 which database to access. This means you can migrate to another SQL database such as PostgreSQL and will only have to install the new MDB2 driver and change a single line of code in your PHP file to be up and running again.

You connect to a MySQL database using MDB2 with code such as the following, where $db_username and the other $db_ variables have already been read in from the login.php file:

require_once 'MDB2.php';

$dsn = "$db_username:$db_password@$db_hostname/$db_database";
$mdb2 = MDB2::connect("mysql://$dsn");

The require_once line loads MDB2. In the next line, the variable $dsn stands for data source name and is an identifier for the database. It comprises username:password@hostname/database. The variable $mdb2 is an object returned by calling the connect method within the MDB2 class. Recall that as mentioned in Chapter 5, the double colon (::) token indicates a class to be used on the left and a method to call from that class to the right.

The full string passed to the connect method is as follows:

mysql://username:password@hostname/database

The mysql:// at the head of ...