??? GetAll() is used to execute queries that return more rows of data, such as when requesting
the list of departments.
??? GetRow() is used to execute queries that return a row data.
??? GetOne() returns a single value from the database. We can use this method to call database
stored procedures that return a single value, such as one that returns the subtotal
of a shopping cart.
Exercise: Creating and Using the DatabaseHandler Class
1. Add the database login information at the end of tshirtshop/include/config.php, modifying the
constants??™ values to fit your server??™s configuration. The following code assumes you created the admin user
account as instructed in Chapter 3:
// Database connectivity setup
define('DB_PERSISTENCY', 'true');
define('DB_SERVER', 'localhost');
define('DB_USERNAME', 'tshirtshopadmin');
define('DB_PASSWORD', 'tshirtshopadmin');
define('DB_DATABASE', 'tshirtshop');
define('PDO_DSN', 'mysql:host=' . DB_SERVER . ';dbname=' . DB_DATABASE);
2. Create a new file named database_handler.php in the tshirtshop/business folder, and create the
DatabaseHandler class as shown in the following code listing. At this moment, we only included its constructor
(which is private, so the class can??™t be instantiated), and the static GetHandler() method, which
creates a new database connection, saves it into the $_mHandler member, and then returns this object
(find more explanations about the process in the upcoming ???How it Works??? section).
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