PHP design pattern Factory (factory pattern)_PHP tutorial

/**
* Factory Method Pattern
*
* Define an interface for creating objects, let subclasses decide which class to instantiate, and use a class to defer instantiation to its subclasses
*/

/*
class DBFactory
{
public static function create($type)
{
swtich($type)
{
case "Mysql":
return new MysqlDB(); break;
case "Postgre":
return new PostgreDB(); break;
case "Mssql":
return new MssqlDB(); break;
}
}
}
*/
class DBFactory
{
public static function create($type)
{
$class = $type."DB";
return new $class;
}
}

interface DB
{
public function connect();
public function exec();
}

class MysqlDB implements DB
{
public function __construct() {
echo "mysql db
";
}

public function connect() {
}

public function exec() {
}
}

class PostgreDB implements DB
{
public function __construct() {
echo "Postgre db
";
}

public function connect() {
}

public function exec() {
}
}

class MssqlDB implements DB
{
public function __construct() {
echo "mssql db
";
}

public function connect() {
}
public function exec() {
}
}

$oMysql = DBFactory::create("Mysql");
$oPostgre = DBFactory::create("Postgre");
$oMssql = DBFactory::create("Mssql");