[Typo3-dev] Change Rootline Language?

[Chi Hoang]

$GLOBALS['TSFE']->sys_language_uid=1;
$GLOBALS["TSFE"]->sys_page->getRootLine($id,$pathMP);

This doesnt work.

Scenario:

I want to change sys_lanuage manually and fetch the rootline with the new
sys_language_uid - but  I get always the same language (the language I
openend the page before). What is wrong?

Greets,

Chi