bit.ly allows users to shorten, share, and track links (URLs). Reducing the URL length makes sharing easier.
PHP Bitly is a (wrapper)class to communicate with bit.ly.
PHP Bitly is BSD licensed.
The class is well documented inline. If you use a decent IDE you'll see that each method is documented with PHPDoc. More documentation can be found on http://classes.verkoyen.eu/bitly/docs.