protected function _connect()
{
  // if we already have a PDO object, no need to re-connect.
  if ($this->_connection) {
    return;
  }
  // get the dsn first, because some adapters alter the $_pdoType
  $dsn = $this->_dsn();
  // check for PDO extension
  if (!extension_loaded('pdo')) {
    /**
     * [url=home.php"sqlsrv:Server=".$this->_config['host'].";Database = ".$this->_config['dbname'], $this->_config['username'], $this->_config['password']);
      $this->_connection->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
      $this->_connection->setAttribute( PDO::SQLSRV_ATTR_ENCODING, PDO::SQLSRV_ENCODING_UTF8 );
      $this->_profiler->queryEnd($q);
    }elseif ($this->_config['pdoType']=='dblib') {
      $this->_connection = new PDO(
        $dsn,
        $this->_config['username'],
        $this->_config['password'],
        $this->_config['driver_options']
      );
      $this->_profiler->queryEnd($q);
    }
    // set the PDO connection to perform case-folding on array keys, or not
    $this->_connection->setAttribute(PDO::ATTR_CASE, $this->_caseFolding);
    // always use exceptions.
    $this->_connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
  } catch (PDOException $e) {
    /**
     * @see Zend_Db_Adapter_Exception
     */
    require_once 'Zend/Db/Adapter/Exception.php';
    throw new Zend_Db_Adapter_Exception($e->getMessage());
  }
}

protected function _dsn()
{
    // baseline of DSN parts
    $dsn = $this->_config;
    // don't pass the username and password in the DSN
    unset($dsn['username']);
    unset($dsn['password']);
    unset($dsn['driver_options']);
    if (isset($dsn['port'])) {
      $seperator = ':';
      if (strtoupper(substr(PHP_OS, 0, 3)) === 'WIN') {
        $seperator = ',';
      }
      $dsn['host'] .= $seperator . $dsn['port'];
      unset($dsn['port']);
    }
    // this driver supports multiple DSN prefixes
    // @see http://www.php.net/manual/en/ref.pdo-dblib.connection.php
    //print_r($dsn);exit;
    if (isset($dsn['pdoType'])) {
      switch (strtolower($dsn['pdoType'])) {
        case 'freetds':
        case 'sybase':
          $this->_pdoType = 'sybase';
          break;
        case 'mssql':
          $this->_pdoType = 'mssql';
          break;
        case 'sqlsrv':
          $this->_pdoType = 'sqlsrv';
          break;
        case 'dblib':
        default:
          $this->_pdoType = 'dblib';
          break;
      }
      unset($dsn['pdoType']);
    }
    // use all remaining parts in the DSN
    foreach ($dsn as $key => $val) {
      $dsn[$key] = "$key=$val";
    }
    $dsn = $this->_pdoType . ':' . implode(';', $dsn);
   // print_r($dsn);exit;
    return $dsn;
}

<db>
  <adapter>PDO_MSSQL</adapter>
<config>
    <host>localhost</host>
    <username>sa</username>
    <password>123456</password>
    <dbname>testdb </dbname>
    <pdoType>sqlsrv</pdoType>
  </config>
</db>

function convert2utf8($string)
{
    $config = $this->getCfg();
    $pdoType = $config->db->config->pdoType;
    if($pdoType == 'dblib'){
      return iconv("gbk","utf-8",$string);
    }elseif($pdoType == 'sqlsrv'){
      return mb_convert_encoding($string,"UTF-8","auto");
    }
}
function convert2gbk($string)
{
    $config = $this->getCfg();
    $pdoType = $config->db->config->pdoType;
    if($pdoType == 'dblib'){
      return iconv("utf-8","gbk",$string);
    }elseif($pdoType == 'sqlsrv'){
      return mb_convert_encoding($string,"GBK","auto");
    }
}
protected function &getCfg() {
    if ($this->cfg_ === null) {
      $registry = Zend_Registry::getInstance();
      $this->cfg_ = $registry->get('web_config');
    }
    return $this->cfg_;
}