Zend FR

// setup Zend_Auth adapter for a database table
Zend_Loader::loadClass('Zend_Auth_Adapter_DbTable');
$dbAdapter = Zend_Registry::get('dbAdapter');
$authAdapter = new Zend_Auth_Adapter_DbTable($dbAdapter);
$authAdapter->setTableName('users');
$authAdapter->setIdentityColumn('username');
$authAdapter->setCredentialColumn('password');

// Set the input credential values to authenticate against
$authAdapter->setIdentity($username);
$authAdapter->setCredential($password);

// do the authentication
$auth = Zend_Auth::getInstance();
$result = $auth->authenticate($authAdapter);

if ($result->isValid())
{
  // success: store database row to auth's storage
  // system. (Not the password though!)
  $data = $authAdapter->getResultRowObject(null, 'password');
  $auth->getStorage()->write($data);
  $this->_redirect('/');
} 
else
{
  // failure: clear database row from session
  $this->view->message = 'Login failed.';
}