Using Pear Auth As Zend Auth Adapter

<?php

class My_Zend_Auth_Adapter_PearAuth implements Zend_Auth_Adapter_Interface
{

    /**
     * The array of arrays of Pear::Auth options passed to the constructor.
     *
     * @var array
     */
    protected $_options = null;

    /**
     * The username of the account being authenticated.
     *
     * @var string
     */
    protected $_username = null;

    /**
     * The password of the account being authenticated.
     *
     * @var string
     */
    protected $_password = null;

    /**
     * The Pear::Auth container.
     *
     * @var string
     */
    protected $_container = null;

    protected $_logger = null;

    /**
     * Constructor
     *
     * @param  string $container The Pear::Auth container to use
     * @param  array $options An array of arrays of Pear::Auth options
     * @param  string $username The username of the account being authenticated
     * @param  string $password The password of the account being authenticated
     * @return void
     */
    public function __construct($container, array $options = array(), $username = null, $password = null)
    {
        $this->setOptions($options);
        if ($username !== null) {
            $this->setUsername($username);
        }
        if ($password !== null) {
            $this->setPassword($password);
        }
        $this->_container = $container;
    }

    public function setLogger($logger)
    {
        $this->_logger = $logger;
    }

    /**
     * Returns the array of arrays of Pear::Auth options.
     *
     * @return array|null
     */
    public function getOptions()
    {
        return $this->_options;
    }

    /**
     * Sets the array of arrays of Pear::Auth options to be used by
     * this adapter.
     *
     * @param  array $options The array of arrays of of Pear::Auth options
     * @return My_Zend_Auth_Adapter_PearAuth Provides a fluent interface
     */
    public function setOptions($options)
    {
        $this->_options = is_array($options) ? $options : array();
        return $this;
    }

    /**
     * Returns the username of the account being authenticated, or
     * NULL if none is set.
     *
     * @return string|null
     */
    public function getUsername()
    {
        return $this->_username;
    }

    /**
     * Sets the username for binding
     *
     * @param  string $username The username for binding
     * @return My_Zend_Auth_Adapter_PearAuth Provides a fluent interface
     */
    public function setUsername($username)
    {
        $this->_username = (string)$username;
        return $this;
    }

    /**
     * Returns the password of the account being authenticated, or
     * NULL if none is set.
     *
     * @return string|null
     */
    public function getPassword()
    {
        return $this->_password;
    }

    /**
     * Sets the password for the account
     *
     * @param  string $password The password of the account being authenticated
     * @return My_Zend_Auth_Adapter_PearAuth Provides a fluent interface
     */
    public function setPassword($password)
    {
        $this->_password = (string)$password;
        return $this;
    }

    /**
     * Authenticate the user
     *
     * @throws Zend_Auth_Adapter_Exception
     * @return Zend_Auth_Result
     */
    public function authenticate()
    {
        require_once 'Pear/Auth.php';

        $messages = array();
        $messages[0] = ''; // reserved
        $messages[1] = ''; // reserved

        $username = $this->_username;
        $password = $this->_password;

        if (!$username) {
            $code = Zend_Auth_Result::FAILURE_IDENTITY_NOT_FOUND;
            $messages[0] = 'A username is required';
            return new Zend_Auth_Result($code, '', $messages);
        }
        if (!$password) {
            /* A password is required because some servers will
            * treat an empty password as an anonymous bind.
            */
            $code = Zend_Auth_Result::FAILURE_CREDENTIAL_INVALID;
            $messages[0] = 'A password is required';
            return new Zend_Auth_Result($code, '', $messages);
        }

        //Override $_POST variables required by Auth pear package.
        $_POST['username'] = $username;
        $_POST['password'] = $password;

        $_auth = new Auth($this->_container, $this->_options, '', false);

        //Enable logging
        if (isset ($this->_options['enableLogging']) && $this->_options['enableLogging'] && !is_null($this->_logger)) {
            $_auth->logger = $this->_logger;
        }

        $_auth->start();

        if ($_auth->getAuth()) {
            //Destroy Pear::Auth session to avoid unespected behaviour
            $_auth->logout();
            $messages[] = "$username authentication successful";
            return new Zend_Auth_Result(Zend_Auth_Result::SUCCESS, $username, $messages);
        }

        $messages[] = "$username authentication failed.";
        return new Zend_Auth_Result(Zend_Auth_Result::FAILURE, $username, $messages);
    }
}

<?php
    ...
    $auth = Zend_Auth::getInstance();
    $config = new Zend_Config_Xml('APPLICATION_HOME/configs/auth_ldap.xml', 'production');
    $options = $config->ldap->toArray();
    $authAdapter = new Zend_Auth_Adapter_PearAuth('LDAP', $options, $username, $password);
    $result = $auth->authenticate($authAdapter);
    if (!is_null($result) && $result->isValid()) {
        $authorized = true;
    }
    ...