Design Patern

Design Patern:  It a formal way of documenting a solution to a problem.

Zend Famework mainly use following Patterns.

Singleton Pattern: It is a design pattern that restricts the instantiation of a class to one object.

 Example: 
class Database {
  private static $_singleton;
  private $_connection;
  
  private function __construct($host,$user,$pass){
    $this->_connection = mysql_connect($host,$user,$pass);
  }

  public static function getInstance(){
   if (is_null (self::$_singleton)) {
   self::$_singleton = new Database();
   }
  return self::$_singleton;
  }
}

$db = Database::getInstance();

Factory Pattern: In this Pattern we can create an instance of any of one class in-directly from an static function of another class.

example 

$db = Zend_Db::factory( ...options... ); 

Implement of factory pattern example