Page 426 - Beginning PHP 5.3

Part III: Using PHP in Practice
Creating the DataObject Class File

Now comes the first of the classes that are used in the application. DataObject is an abstract class from
which you can derive classes to handle database access and data retrieval. Because it ’ s an abstract class,
you can ’ t instantiate (create objects from) it directly. In a moment, you create classes to handle both
members and access log records that are based on the DataObject class.

In OOP parlance, these types of classes are said to follow the active record design pattern, which means
that the object contains the data for the record to store in or retrieve from the database, as well as the
methods to carry out the actual storage and retrieval.

Save the following script as DataObject.class.php in the book_club folder:

< ?php

require_once “config.php”;

abstract class DataObject {

protected $data = array();

public function __construct( $data ) {
foreach ( $data as $key = > $value ) {
if ( array_key_exists( $key, $this- > data ) ) $this- > data[$key] =
$value;
}
}

public function getValue( $field ) {
if ( array_key_exists( $field, $this- > data ) ) {
return $this- > data[$field];
} else {
die( “Field not found” );
}
}

public function getValueEncoded( $field ) {
return htmlspecialchars( $this- > getValue( $field ) );
}

protected function connect() {
try {
$conn = new PDO( DB_DSN, DB_USERNAME, DB_PASSWORD );
$conn- > setAttribute( PDO::ATTR_PERSISTENT, true );
$conn- > setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
} catch ( PDOException $e ) {
die( “Connection failed: “ . $e- > getMessage() );
}

return $conn;
}

protected function disconnect( $conn ) {

388

9/21/09 9:12:02 AM
c13.indd 388
c13.indd 388 9/21/09 9:12:02 AM