Handles AuthSub, requests, etc. Includes a sample application that the developer built for working with GCal.

PHP4 OAuth

https://svn.iamcal.com/public/php/lib_oauth/lib_oauth.php

Cal Henderson’s super lightweight OAuth library, compatible with PHP4.

PHP XML Library

http://keithdevens.com/software/phpxml#source

Could this finally be what I’ve been looking for? A generic XML-parsing library, written in PHP, which handles namespaces and attributes reasonably elegantly?

coreylib

http://aaroncollegeman.com/projects/coreylib/

coreylib

“coreylib is a PHP library for accessing Web service APIs like Twitter. You can use coreylib to explore APIs, cache their content, create mash-ups, and style the output.”

PHP.JS

http://phpjs.org/

PHP.JS

“PHP.JS is an open source project in which we try to port PHP functions to JavaScript. By including the PHP.JS library in your own projects, you can use your favorite PHP functions client-side.”

Ident Engine

http://identengine.com/

Ident Engine

“Without much conscious thought, most of us have built identities across the web. We’ve filled in profiles, uploaded photos, videos, reviews and bookmarks. The Ident Engine uses semantic web API’s to bring together these web footprints.”