The Google Data API support comes with a few gotchas. Its documentation show a clear preference for using GET instead of POST, though the Google OAuth server does appear to natively support POST requests for everything with the exception that it has a small bug which interprets an empty POST request body as a sort of phantom empty parameter.

He notes that the library he's been working on (and submitted to both the Zend Framework and PEAR) it up to the 0.0.3 release including functionality marked as beta for the Consumer portion.

Yes, my OpenID 2.0 PHP5 Consumer has finally been proposed to PEAR. This brings the OpenID fanaticism on PEAR to four packages: OpenID_Consumer, Services_Yadis, Crypt_HMAC2, Crypt_DiffieHellman.

He'll be working to get the code "further up to par" including Nonce validation, more consistent error reporting and other operation modes (like check_immediate). He's also included a screencast in the post for those not familiar with OpenID to get their first dose.

This provides a PHP5 implementation of the Yadis Specification 1.0 a requirement of the OpenID Authentication 2.0 Specification. There are way too many specifications out there! The proposal is a reflection of February's "Zend_Service_Yadis" proposal to the Zend Framework. The main differences (beside the PEARification) were fixing the main bugs the ZF sample code had.

He also mentions his next proposal - to create an OpenID Consumer package.