php——資料庫連接的偽單例模式代碼

各位redis群的同學，幫忙查看指正一下代碼，多謝了，希望看到各位的改進意見

<?phpclass Singleton{// MYSQL資料庫連接資訊const MYSQLHOSTNAME = "127.0.0.1";const MYSQLCHARSET = "utf8";private static $instances = array(); //偽類單例private $db; //資料庫連接控制代碼/** * Description:私人化建構函式，防止外界執行個體化對象 */private function __construct($dbname, $username, $password){//串連資料庫$this->db = new mysqli(self::MYSQLHOSTNAME, $username, $password, $dbname);$this->db->set_charset(self::MYSQLCHARSET);if (mysqli_connect_errno()){throw new CircleMysqlException("error", 1000);}}/** * Description:私人化複製函數，防止外界複製對象 */private function __clone(){}/** * Description:靜態方法，單例訪問統一入口 * @return Singleton：返回應用中的唯一對象執行個體 */public static function GetInstance($dbname, $username, $password){$hash = (string) $dbname;if (!isset(self::$instances[$hash])){self::$instances[$hash] = new self($dbname, $username, $password);}return self::$instances[$hash];}/** * Description:擷取資料庫的私人方法的串連控制代碼 */public function GetDbConnect(){return $this->db;}/** * Description:關閉資料庫連結的方法 */public function CloseDbConnect($dbname){$hash = (string) $dbname;self::$instances[$hash]->db->close();unset(self::$instances[$hash]);}}