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The Template Pattern - PHP

Last week, we began our overview of the object-oriented features of PHP 5. This week, we will start discussing design patterns. This article, the second of several parts, is excerpted from chapter two of the book Advanced PHP Programming, written by George Schlossnagle (Sams; ISBN: 0672325616).

  1. Design Patterns and PHP 5
  2. The Adaptor Pattern
  3. More on the Adapter Pattern
  4. The Template Pattern
By: Sams Publishing
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September 28, 2006

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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:

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_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.

>>> More PHP Articles          >>> More By Sams Publishing

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