On PHPBuilder.com today there's a tutorial introducing you to OAuth and how to use it in your PHP applications.

Oauth is an open standard for authorization that allows secure authorization from web, mobile and desktop applications. This standard allows a third-party application to gain access to a HTTP service, i.e. it enables users to share their resources from one website with another website without having to give out their credentials (usually username and password). [...] Oauth authorization is carried out in 3 steps: obtain a request token, authorize request token and exchange request token for an access token.

They introduce you to some of the basic concepts behind OAuth and how the process works (complete with a handy graphic). They then show how to use OAuth to connect to the Facebook API, both in Javascript then PHP. This is followed with two other examples referencing popular social sites Twitter and Foursquare, hitting their APIs with simple authentication requests.

On the PPI framework blog there's a recent post showing how to use the framework to create geolocation functionality via an interface with FourSquare and Google Maps.

In this article, we're going to learn how to work with the framework as a whole by writing a real-world application: making a module, controller, routes, templates (views) and services. In order to achieve this we are will use the Foursquare API, and APC for caching the API lookups. We will plot venues from Foursquare in Google Maps for display.

They help you set up a skeleton application and start on creating the "Foursquare Module" along with its controller and views. There's Javascript code included to use the Google Maps functionality and a simple class to work with the FourSquare API to get nearby venues. In the end, you'll have a basic application that maps out the points automatically.

In a new post to his blog James Morris has shared a custom Symfony2 console command he's written to pull in Foursquare data for his testing locally.

I've been playing with the Foursquare API recently, I'm attempting to get a new homepage built and want to display a map of where I hang out. I use Foursquare quite a bit so wanted to get the locations from their API then plot them on Google maps. There's a venuehistory endpoint that gives you a massive list of all the venues you've checked into with details such as the venue name, location including lat and lng coordinates, and the count of times you've checked in.

He includes a screenshot of the API's results, the code you'll need to recreate it and an example of it running.