Unfortunately, plugin developer use of the new WP 3.1 admin system column sorting feature described above was disabled in WP 3.1RC3 due to a large number of bugs discovered during testing and the capability won’t be included in the final release. This is the text of the official notice about that:

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The biggest change is the removal of AJAX list tables, which had been an effort to move all of our list-style screens to full AJAX for pagination, searches, and column sorts, and to consolidate the list-style screens into a single API that plugins could leverage. Unfortunately, with more testing came realizations that there were too many major bugs and usability issues with how the functionality was implemented, so we’ve spent the last week rolling back the most important portions of the feature.

■For users: AJAX has been entirely disabled for the list tables. We hope to bring this back again, in a form that is properly and fully implemented, in a future release. Column sorting remains, but everything else has returned to its 3.0 state.

■For developers: The entire list table API is now marked private. If you attempt to leverage new components of the API, you are pretty much guaranteeing that your plugins will break in a future release, so please don’t do that. We hope to enable all the fun new goodies for public use in a future release.

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