问zend中的多用户密码相同

EN

class MyAuthAdapter implements Zend_Auth_Adapter_Interface
{
    protected $_username;
    protected $_password;
    protected $_assignment_id;

    /**
     * Sets username, password, and assignemnt ID for authentication
     *
     * @return void
     */
    public function __construct($username,$password,$assignment_id)
    {
        $this->_username = $username;
        $this->_password = $password;
        $this->_assignment_id = $assignment_id;
    }

    /**
     * Performs an authentication attempt
     *
     * @throws Zend_Auth_Adapter_Exception If authentication cannot
     *                                     be performed
     * @return Zend_Auth_Result
     */
    public function authenticate()
    {
        // logic here to check everything out and erturn a new Zend_Auth_Result     
    }
}