Yii Playground Error

hi all, i get this error for yii playground:


 		CDbConnection failed to open the DB connection: could not find driver	


<?php

/**

* This is the base config file.  Other config files may extend this.  See development.php

*/




// uncomment the following to define a path alias

// Yii::setPathOfAlias('local','path/to/local-folder');




// Common Jui Widget preferences:

$jui_prefs =array(

	'themeUrl'=>'css/jui/',

	'theme'=>'base',

);




// This is the main Web application configuration. Any writable

// CWebApplication properties can be configured here.

return array(

	'basePath'=>dirname(__FILE__).DIRECTORY_SEPARATOR.'..',

	'name'=>'Yii Playground',


	// preloading 'log' component

	'preload'=>array('log', 'dbManager', 'uiSettings', 'lc'),


	// autoloading model and component classes

	'import'=>array(

		'application.models.*',

		'application.components.*',

	),




	'localeDataPath'=>'protected/i18n/data/',


	// application components

	'components'=>array(

		'user'=>array(

			// enable cookie-based authentication

			'allowAutoLogin'=>true,

		),

		'uiSettings'=>array(

			'class'=>'UiSettings',

		),

		'db'=>array(

			'autoConnect'=>false, // we will activate the connection from dbManager

			'connectionString' => '', // we set connectionString from dbManager

			'tablePrefix'=>'tbl_',

		),

		'sc'=>array(

			'class' => 'application.components.SrcCollect',

		),

		'dbManager'=>array(

			'class' => 'application.components.DbManager',

		),

		'lc'=>array(

			'class' => 'application.components.LocaleManager',

		),

		// uncomment the following to use a MySQL database

		/*

		'db_mysql'=>array(

			'connectionString' => 'mysql:host=localhost;dbname=testdrive',

			'emulatePrepare' => true,

			'username' => 'root',

			'password' => '',

			'charset' => 'utf8',

		),

		*/

		'errorHandler'=>array(

			// use 'site/error' action to display errors

			'errorAction'=>'site/error',

		),

		'widgetFactory' => array(

			'widgets' => array(

				'CJuiDialog' => $jui_prefs,

				'CJuiTabs' => $jui_prefs,

				'CJuiDatePicker' => $jui_prefs,

				'CJuiAutoComplete' => $jui_prefs,

			),

		),

		'log'=>array(

			'class'=>'CLogRouter',

			'routes'=>array(

				array(

					'class'=>'CFileLogRoute',

					'levels'=>'error, warning',

				),

			),

		),

	),

	

	'modules' => array(

		'AjaxModule',

		'UiModule',

		'InternationalizationModule',

		'SecurityModule',

		'ExtensionModule',

	),


	// application-level parameters that can be accessed

	// using Yii::app()->params['paramName']

	'params'=>array(

		// this is used in contact page

		'adminEmail'=>'webmaster@example.com',

		'factory_db'=>'protected/data/factory.db',

		'user_db'=>'protected/data/user.db',

		'database_format'=>array(

			'date'=>'yyyy-MM-dd',

			'time'=>'HH:mm:ss',

			'dateTimeFormat'=>'{1} {0}',

		),

	),

);