application.ini:

resources.db.adapter = PDO_MYSQL
resources.db.adapter.params.host = ...
resources.db.adapter.params.username = ..
resources.db.adapter.params.password = ...
resources.db.adapter.params.dbname = ...


Bootstrap.php:

    protected function _initDb()
    {
        $db = Zend_Db::factory(new Zend_Config($this->getOptions()));
        Zend_Registry::set('db', $db);
    }