oAuth class file is missing from library

I am trying to develop Yahoo oAuth in PHP. I downloaded script from

oauth examples. But when i am running request_token.php it giving me following error. I problem is i don't have oauth class.

$o = new OAuth(OAUTH_CONSUMER_KEY, OAUTH_CONSUMER_SECRET, OAUT here an error is coming

Fatal 开发者_JS百科error: Class 'OAuth' not found

Where can i download complete oauth library for PHP.

Thank You

That example was taken from http://svn.php.net/viewvc/pecl/oauth/trunk/examples/yahoo/, which is a directory belonging to the oauth PECL extension, so I'd start looking there.