Book Image

Learning PHP Data Objects

By : Dennis Popel
Book Image

Learning PHP Data Objects

By: Dennis Popel

Overview of this book

PDO is lighter, faster, and more powerful than existing PHP data abstraction interfaces. PDO is a common interface to different databases that must be used with a database-specific PDO driver to access a particular database server: the PDO extension does not provide a database abstraction by itself; it doesn't rewrite SQL, emulate missing database features, or perform any database functions using by itself. It performs the same role as other classic database abstraction layers such as ODBC and JDBC: it's a query abstraction layer that abstracts the mechanism for accessing a database and manipulating the returned records; each database driver that implements the PDO interface can also expose database-specific features as regular extension functions. ¬ PDO ships with PHP 5.1, and is available as an extension for PHP 5.0; it requires the new object-oriented features of PHP 5, and cannot run with earlier versions of PHP.This book will teach you how to use the PDO, including its advanced features. Readers need to be aware of the basics of data abstraction and should be familiar with PHP.
Table of Contents (13 chapters)

MySQL Buffered Queries

If you are working with a MySQL database only, then you may want to employ MySQL's PDO driver buffered query mode. When the connection is set to the buffered query mode, the whole result set for every SELECT query is pre-fetched into memory before it is returned to the application. This gives us one benefit—we can use the PDOStatement::rowCount() method to inspect how many rows the result set contains. In Chapter 2, we discussed this method and showed that it returns 0 for MySQL and SQLite databases. Now, when PDO is instructed to use buffered queries, this method will return meaningful values.

To force PDO into MySQL buffered query mode, you have to specify the PDO::MYSQL_ATTR_USE_BUFFERED_QUERY connection attribute. Consider the following example:

$conn = new PDO($connStr, $user, $pass);
$conn->setAttribute(PDO::MYSQL_ATTR_USE_BUFFERED_QUERY, 1);
$q = $conn->query("SELECT * FROM books");