Tonight Facebook announced that they made a few changes to application iframe canvas pages which “provide them with more of the functionality previously available only to FBML-based applications.” This means that applications will now be able to use XFBML, an extension of FBML which works on iFrame pages. These features also give application developers access to cached friend lists and preload FQL data.

There are a few other changes as well:

In addition to the JavaScript client library changes, iframe applications that want to preload FQL queries will receive the data along with other parameters via POST with the prefix ‘fb_post_sig’. We’re using a different prefix from the original ‘fb_sig’ prefix so we can avoid namespace collisions with the GET parameters, which will continue to use ‘fb_sig’ for compatibility with current applications which may be expecting the data. These parameters can be accessed and validated in the same method as the old parameters (for the PHP client, use get_valid_fb_params with the new fb_post_sig prefix).

For more information on the update, check out the Facebook post to developers.