php的单例模式

<?phpclass Mysql { ???private $conn; ???private static $instance =null; ???private function __construct(){ ???????$conn = @mysql_connect(‘localhost‘,‘root‘,‘root‘); ???} ???//单例模式 ???public ?static function getInstance (){ ???????if(! self::$instance instanceof self){ ???????????self::$instance = new self; ???????} ???????return self::$instance; ????????} ????//防止克隆 ???private function __clone(){}}$mysql ?= Mysql::getInstance();$mysql2 ?= Mysql::getInstance();var_dump($mysql);echo ‘<hr>‘;var_dump($mysql2);