The Zend Developer Zone article Using the Twitter API with PHP and PEAR covers the Services_Twitter PEAR package, which the articles describes as follows:
Services_Twitter works by providing a full-fledged, object-oriented interface to the Twitter API. This interface insulates you from the nitty-gritty of working directly with REST requests and, by representing responses as SimpleXML objects, makes it very easy to access specific elements of the returned data. This not only saves time; it’s also simpler, because it’s no longer necessary to be intimately aware of the nitty-gritties of the Twitter API in order to use it effectively.