Now that you're comfortable using the MySQL client tools to manipulate data in the database, you can begin using PHP to display and modify data from the database. PHP has standard functions for working with the database.
First, we're going to discuss PHP's built-in database functions. We'll also show you how to use the The PHP Extension and Application Repository (PEAR) database functions that provide the ability to use the same functions to access any supported database. This type of flexibility comes from a process called abstraction. In programming interfaces, abstraction simplifies a complex interaction. It works by removing any nonessential parts of the interaction, allowing you to concentrate on the important parts. PEAR's DB classes are one such database interface abstraction. The information you need to log into a database is reduced to the bare minimum. This standard format allows you to interact with MySQL, as well as other databases using the same functions. Similarly, other MySQL-specific functions are replaced with generic ones that know how to talk to many databases. For example, the MySQL-specific connect function is:
mysql_connect($db_host, $db_username, $db_password);
versus PEAR's DB connect function:
$connection = DB::connect("mysql://$db_username:[email protected]$db_host/$db_database");
The same basic information is present in both commands, but the PEAR function also specifies the type of databases to which to connect. You can connect to MySQL or other supported databases. We'll discuss both connection methods in detail.
In this chapter, you'll learn how to connect to a MySQL server from PHP, how to use PHP to access and retrieve stored data, and how to correctly display information to the user.
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