php|architect has officially announced the release of their latest book: Integrating Web Services with OAuth and PHP from author and PHP community member Matt Frost.
Modern web applications are no longer standalone, monolithic codebases. Instead, they are expected to integrate with external, 3rd party applications to allow users to tap into new features, integrate with their social networks, and to easily migrate their data between systems. Many services afford these integrations by building web services that use the OAuth standard to authenticate users and allow “secure delegated access” on their behalf.
The book covers both of the major versions of OAuth currently in use (v1 and v2), how they differ and provides working PHP examples of both the client and server sides of the functionality. If you're interested you can "try before you buy" with an excerpt from the book to get a feel for the writing style and content. You can get more information and pick up a copy of your own directly from the php[architect] site.