Where to start with Google Reader as an API?

I want to build a widget for WordPress that simultaneously displays my latest Google Reader items on the front page and allows for management from behind the WordPress dashboard. I can already add my "shared" items using code I've found in various Google searches, but that's not exact开发者_StackOverflow中文版ly what I'm looking for.

I like the functionality of the Google Reader widget in iGoogle, and I want to replicate that on the WordPress dashboard and build a read-only version for the WordPress front-end. Where do I start in the API (public or 'unofficial') to get this built?

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I've found some limited documentation regarding authentication protocols, but I've been unable to implement anything. I can parse a URL to authenticate and get an SSID that works when directly placed in a browser, but both GET and POST requests fail via PHP, so I can't get any further than that.

-- Update --

I've converted the first few steps of Martin Doms' C# tutorial into PHP for anyone who's interested in doing this on their own site.

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Here's a nice 3-step tutorial: http://blog.martindoms.com/2009/08/15/using-the-google-reader-api-part-1/

If you're having problems from PHP, then I think you should post the PHP code to see where it's failing. These steps should work flawlessly.

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I can add some extra resources, especially the ones that resemble the most a structured documentation for this unofficial API:

• http://code.google.com/p/pyrfeed/wiki/GoogleReaderAPI - Very good and structured API documentation.
• http://blog.martindoms.com/2009/10/16/using-the-google-reader-api-part-2 - (Already referred above) Also a well structured API documentation, in 3 parts. Contains some details not seen elsewhere.
• http://www.chrisdadswell.co.uk/android-coding-example-authenticating-clientlogin-google-reader-api/ - Good resource for coding examples and API documentation
• http://groups.google.com/group/fougrapi/ - 'Official' group for the unofficial Google Reader API. Lots of advanced questions, often answered by Google developers. Not good for structured documentation though...

Hope it helps!

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Following up on EAMann his PHP class is here http://code.google.com/p/greader-library/source/browse/trunk/greader.class.php?r=4. I got it working last night. Thank you Eric, I will be adding to your library.