ZF如何连接MSSQL 2005?

[chengsyz]

项目需要ZF连接MSSQL2005，我是按这样写的:

$this->params = array ( 'host' => 'localhost',
'username' => 'sa',
'password' => '12345abc',
'dbname' => 'test');

$db = Zend_Db::factory('PDO_Mssql', $this->params);

php.ini中 extension=php_pdo.dll 和 extension=php_pdo_mssql.dll 都启用了，无法连接数据库，报错如下:

"The mssql driver is not currently installed"

如何解决啊？