Programming PHP, 4th Edition

Chapter 9. Databases

PHP has support for over 20 databases, including the most popular commercial and open source varieties. Relational database systems such as MariaDB, MySQL, PostgreSQL, and Oracle are the backbone of most modern dynamic websites. In these are stored shopping-cart information, purchase histories, product reviews, user information, credit card numbers, and sometimes even web pages themselves.

This chapter covers how to access databases from PHP. We focus on the built-in PHP Data Objects (PDO) library, which lets you use the same functions to access any database, rather than on the myriad database-specific extensions. In this chapter, you’ll learn how to fetch data from the database, store data in the database, and handle errors. We finish with a sample application that shows how to put various database techniques into action.

This book cannot go into all the details of creating web database applications with PHP. For a more in-depth look at the PHP/MySQL combination, see Web Database Applications with PHP and MySQL, Second Edition (O’Reilly), by Hugh Williams and David Lane.

Using PHP to Access a Database

There are two ways to access databases from PHP. One is to use a database-specific extension; the other is to use the database-independent PDO library. There are advantages and disadvantages to each approach.

If you use a database-specific extension, your code is intimately tied to the database you’re using. For example, the MySQL extension’s function names, ...