<"恭喜您，mysql数据库连接成功";
  }
  public function add(){
  }
  public function delete(){
  }
  public function update(){
  }
  public function select(){
  }
  public function getLastSql(){
  }
}
/**
 * @desc 创建sqlServerDb 类
 * **/
class sqlServerDb implements DB{
  public function conn(){
    echo "恭喜您，sqlServer数据库连接成功";
  }
  public function add(){
  }
  public function delete(){
  }
  public function update(){
  }
  public function select(){
  }
  public function getLastSql(){
  }
}
/**
 * @desc 创建一个数据库工程类，用来生产对象
 * **/
class DbFactory{
  static $db = null;
  public static function getDb($type){
    switch($type){
      case 'mysql':
        self::$db = new mysqlDb();
        break;
      case 'sqlServer':
        self::$db = new sqlServerDb();
        break;  
    }
    return self::$db;
  }
}
//测试使用mysql来连接数据库测试工程模式是否成功
$factory = new DbFactory();
$db = $factory->getDb('mysql');
$db->conn();