Where to start with Google Reader as an API?
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.
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!
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.