[TYPO3-english] Changing logged-in FE user's usergroup within extension

[Jörg Wagner]

I am changing the usergroup of a logged-in FE user on the fly from 
within an extension.
To do this I update the usergroup value in table 'fe_users' and - to 
really play it safe - I also update 
$GLOBALS['TSFE']->fe_user->user['usergroup'] with the same new value.

Basically everything works fine, except for the fact that the next page 
that is rendered after the change still behaves as if the old usergroup 
was set. Any page elements that should only be visible for the old 
usergroup stay visible until I reload the page. The page is rendered 
with no-cache headers (it also coutains an fe-login form which forces 
these headers). So it should not be a caching issue.

I am searching my ass off how to update the page content directly, so 
that the next visible page reflects the usergroup change of the active user.
Any help is much appreciated!