An example of using Zend_Db_Adapter_* as the storage connector for OAuth2 library at https://github.com/zircote/oauth2-php

OAuth2\ZendDb.php

<?php
/**
 * @category   Cautela
 * @package    Auth
 * @subpackage OAuth2
 */
namespace Auth\OAuth2;
use OAuth2\Grant\GrantCodeInterface;
use OAuth2\RefreshTokensInterface;
use Zend_Db_Adapter_Abstract;
use Zend_Db_Exception;

/**
 *
 * @category   OAuth2
 * @package    Auth
 * @subpackage OAuth2
 */
class ZendDb implements GrantCodeInterface, RefreshTokensInterface
{
    /**
     * Database table names
     *
     * @var array
     */
    protected $_tableMap = array(
        'clients'        => 'clients',
        'auth_code'      => 'auth_code',
        'access_tokens'  => 'access_tokens',
        'refresh_tokens' => 'refresh_tokens'
    );

    /**
     * @var Zend_Db_Adapter_Abstract
     */
    protected $_db;

    /**
     *
     */
    public function __construct(Zend_Db_Adapter_Abstract $db)
    {

        try {
            $this->db = $db;
        } catch (Zend_Db_Exception $e) {
            die('Connection failed: ' . $e->getMessage());
        }
    }

    /**
     * @param array $tableMap
     * @return ZendDb
     */
    public function setTableMap(array $tableMap)
    {
        $this->_tableMap = $tableMap;
        return $this;
    }
    /**
     * @return Zend_Db_Adapter_Abstract
     */
    public function getDb()
    {
        return $this->_db;
    }

    /**
     * @param Zend_Db_Adapter_Abstract $db
     * @return ZendDb
     */
    public function setDb(Zend_Db_Adapter_Abstract $db)
    {
        $this->_db = $db;
        return $this;
    }

    /**
     *
     */
    protected function handleException(\Exception $e)
    {
        throw $e;
    }

    /**
     *
     * @param string $client_id     Client identifier to be stored.
     * @param string $client_secret Client secret to be stored.
     * @param string $redirect_uri  Redirect URI to be stored.
     * @return ZendDb
     */
    public function addClient($client_id, $client_secret, $redirect_uri)
    {
        try {
            $client_secret = $this->hash($client_secret, $client_id);
            $data          = array(
                'client_id'     => $client_id,
                'client_secret' => $client_secret,
                'redirect_uri'  => $redirect_uri
            );
            $this->getDb()->insert($this->_tableMap['clients'], $data);
        }
        catch (Zend_Db_Exception $e) {
            $this->handleException($e);
        }
        return $this;
    }

    /**
     * @param string      $client_id
     * @param null|string $client_secret
     * @return bool
     */
    public function checkClientCredentials($client_id, $client_secret = null)
    {
        try {
            $sql = $this->getDb()->select()
                ->from($this->_tableMap['clients'], 'client_secret')
                ->where($this->getDb()->quoteInto('client_id = ?', $client_id));

            $hashed_secret = $this->getDb()->fetchOne($sql);

            if ($client_secret === null) {
                return $hashed_secret !== false;
            }

            return $this->checkPassword(
                $client_secret, $hashed_secret, $client_id
            );
        }
        catch (Zend_Db_Exception $e) {
            $this->handleException($e);
        }
        return false;
    }

    /**
     * @param $client_id
     * @return bool|string|void
     */
    public function getClientDetails($client_id)
    {
        try {
            $sql = $this->getDb()->select()
                ->from($this->_tableMap['clients'], 'redirect_uri')
                ->where($this->getDb()->quoteInto('client_id = ?', $client_id));

            $redirect_uri = $this->getDb()->fetchOne($sql);


            if ($redirect_uri === false) {
                return $redirect_uri !== false;
            }
        }
        catch (Zend_Db_Exception $e) {
            $this->handleException($e);
        }
        return null;
    }

    /**
     * @param string $oauth_token
     * @return array|null
     */
    public function getAccessToken($oauth_token)
    {
        return $this->getToken($oauth_token, false);
    }

    /**
     * @param string $oauth_token
     * @param string $client_id
     * @param string $user_id
     * @param string $expires
     * @param null   $scope
     * @return ZendDb
     */
    public function setAccessToken($oauth_token, $client_id, $user_id, $expires,
                                   $scope = null)
    {
        return $this->setToken(
            $oauth_token, $client_id, $user_id, $expires, $scope, false
        );
    }

    /**
     * @param string $refresh_token
     * @return array|null
     */
    public function getRefreshToken($refresh_token)
    {
        return $this->getToken($refresh_token, true);
    }

    /**
     * @param string      $refresh_token
     * @param string      $client_id
     * @param string      $user_id
     * @param string      $expires
     * @param null        $scope
     * @return ZendDb
     */
    public function setRefreshToken($refresh_token, $client_id, $user_id,
                                    $expires, $scope = null)
    {
        return $this->setToken(
            $refresh_token, $client_id, $user_id, $expires, $scope, true
        );
    }

    /**
     * @param string $refresh_token
     * @return ZendDb
     */
    public function unsetRefreshToken($refresh_token)
    {
        try {
            $this->getDb()->delete(
                $this->_tableMap['refresh_tokens'],
                $this->getDb()->quoteInto('refresh_token = ?', $refresh_token)
            );
        }
        catch (Zend_Db_Exception $e) {
            $this->handleException($e);
        }
        return $this;
    }

    /**
     * @param string $code
     * @return array|null
     */
    public function getAuthCode($code)
    {
        try {
            $sql    = $this->getDb()->select()
                ->from(
                $this->_tableMap['auth_codes'], array(
                                                     'code', 'client_id',
                                                     'user_id', 'redirect_uri',
                                                     'expires', 'scope'
                                                )
            )
                ->where($this->getDb()->quoteInto('code = ?', $code));
            $result = $this->getDb()->fetchRow($sql);

            return $result !== false ? $result : null;
        }
        catch (Zend_Db_Exception $e) {
            $this->handleException($e);
        }
        return null;
    }

    /**
     * @param string     $code
     * @param string     $client_id
     * @param string     $user_id
     * @param string     $redirect_uri
     * @param string     $expires
     * @param null       $scope
     * @return ZendDb
     */
    public function setAuthCode($code, $client_id, $user_id, $redirect_uri,
                                $expires, $scope = null)
    {
        try {
            $data = array(
                'code'    => $code, 'client_code' => $client_id,
                'user_id' => $user_id, 'redirect_uri' => $redirect_uri,
                'expires' => $expires, 'scope' => $scope
            );
            $this->getDb()->insert($this->_tableMap['auth_codes'], $data);
        }
        catch (Zend_Db_Exception $e) {
            $this->handleException($e);
        }
        return $this;
    }

    /**
     * @deprecated
     *
     * @param string $client_id
     * @param string $grant_type
     * @return bool
     */
    public function checkRestrictedGrantType($client_id, $grant_type)
    {
        return true;
    }

    /**
     * Creates a refresh or access token
     *
     * @param string $token - Access or refresh token id
     * @param string $client_id
     * @param mixed  $user_id
     * @param int    $expires
     * @param string $scope
     * @param bool   $isRefresh
     * @return ZendDb
     */
    protected function setToken($token, $client_id, $user_id, $expires, $scope,
                                $isRefresh = true)
    {
        try {
            $data = array(
                'token'   => $token, 'client_id' => $client_id,
                'user_id' => $user_id, 'expires' => $expires, 'scope' => $scope
            );

            $this->getDb()->insert(
                $isRefresh ? $this->_tableMap['refresh_tokens'] :
                    $this->_tableMap['access_tokens'], $data
            );
        }
        catch (Zend_Db_Exception $e) {
            $this->handleException($e);
        }
        return $this;
    }

    /**
     * Retrieves an access or refresh token.
     *
     * @param string $token
     * @param bool   $refresh
     */
    protected function getToken($token, $isRefresh = true)
    {
        try {
            $tableName = $isRefresh ? $this->_tableMap['refresh_tokens'] :
                    $this->_tableMap['access_tokens'];
            $tokenName = $isRefresh ? 'refresh_token' : 'oauth_token';

            $sql = $this->getDb()->select()
                ->from(
                $tableName,
                array($tokenName, 'client_id', 'expires', 'scope', 'user_id')
            )->where($this->getDb()->quoteInto('token = ?', $token));

            $result = $this->getDb()->fetchRow($sql);

            return $result !== false ? $result : null;
        }
        catch (Zend_Db_Exception $e) {
            $this->handleException($e);
        }
        return null;
    }

    /**
     *
     * @param string $secret
     * @return string
     */
    protected function hash($client_secret, $client_id)
    {
        return hash('blowfish', $client_id . $client_secret);
    }

    /**
     *
     * @param string $client_id
     * @param string $client_secret
     * @param string $actualPassword
     */
    protected function checkPassword($try, $client_secret, $client_id)
    {
        return $try == $this->hash($client_secret, $client_id);
    }
}

https://github.com/zircote/oauth2-php