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.

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Learning PHP Data Objects
Dennis Popel
Aug, 2007 | 188 pages
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Table of Contents (13 chapters)
Learning PHP Data Objects
Learning PHP Data Objects
Credits
Credits
About the Author
About the Author
About the Reviewers
About the Reviewers
Preface
Preface
Free Chapter
1
Introduction
Introduction
Using PDO
Summary
2
Using PHP Data Objects: First Steps
Using PHP Data Objects: First Steps
Connection Strings
Designing Our Code
PDO Statements and Result Sets
Retrieving Result Set Metadata
Summary
3
Error Handling
Error Handling
Sources of Errors
Types of Error Handling in PDO
Defining an Error Handling Function
Creating the Edit Book Page
Creating the Edit Author Page
Securing against Uncaught Exceptions
Summary
4
Prepared Statements
Prepared Statements
Prepared Statements
Working with BLOBs
Summary
5
Handling Rowsets
Handling Rowsets
Retrieving the Number of Rows in a Result Set
Limiting the Number of Rows Returned
Summary
6
Advanced PDO Usage
Advanced PDO Usage
Setting and Getting Connection Attributes
MySQL Buffered Queries
Connecting Using the Connection Configuration File and php.ini Setting
Getting the List of Available Drivers
Transactions
Summary
7
An Advanced Example
An Advanced Example
Designing the Model
Modifying the Frontend to Use the Model
Advantages of Separating the Model
Further Thoughts
Finishing Up
Introduction to OOP in PHP5
Introduction to OOP in PHP5
What is Object-Oriented Programming?
The Advantages of OOP
Static Properties, Methods, and Class Constants
Exceptions
Summary

Retrieving the Number of Rows in a Result Set

As we have already discussed in Chapter 2, the PDOStatement::rowCount() method does not return the correct number of rows in a query. (It returns zero for both MySQL and SQLite.) The reason for such behavior is that the database management systems do not actually know this number until the last row of the query has been returned. The reason for the mysql_num_rows() function (and similar functions for other databases) returns the row count is that it preloads the whole result set into memory when you issue the query.

While it may seem convenient, this behavior is not recommended. If the query returns 20 rows, then the script can afford the memory usage. But what if the query returns several hundred thousands rows? They will all be kept in memory so that, on high traffic sites, the server may run out of resources.

The only logical measure (and the only option available with PDO) is to instruct the database to count the number of rows itself. No...

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