Design Patterns and PHP 5 - The Template Pattern
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The Template pattern describes a class that modifies the logic of a subclass to make it complete.
You can use the Template pattern to hide all the database-specific connection parameters in the previous classes from yourself. To use the class from the preceding section, you need to constantly specify the connection parameters:
<?php
require_once 'DB.inc';
define('DB_MYSQL_PROD_USER', 'test');
define('DB_MYSQL_PROD_PASS', 'test');
define('DB_MYSQL_PROD_DBHOST', 'localhost');
define('DB_MYSQL_PROD_DBNAME', 'test');
$dbh = new DB::Mysql(DB_MYSQL_PROD_USER,
DB_MYSQL_PROD_PASS,
DB_MYSQL_PROD_DBHOST,
DB_MYSQL_PROD_DBNAME);
$stmt = $dbh->execute("SELECT now()");
print_r($stmt->fetch_row());
?>
To avoid having to constantly specify your connection parameters, you can subclass DB_Mysql and hard-code the connection parameters for the test database:
class DB_Mysql_Test extends DB_Mysql {
protected $user = "testuser";
protected $pass = "testpass";
protected $dbhost = "localhost";
protected $dbname = "test";
public function _ _construct() { }
}
Similarly, you can do the same thing for the production instance:
class DB_Mysql_Prod extends DB_Mysql {
protected $user = "produser";
protected $pass = "prodpass";
protected $dbhost = "prod.db.example.com";
protected $dbname = "prod";
public function _ _construct() { }
}
Please check back next week for the continuation of this article.
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 This article is excerpted from chapter two of the book Advanced PHP Programming, written by George Schlossnagle (Sams; ISBN: 0672325616). Check it out today at your favorite bookstore. Buy this book now.
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