[TYPO3-english] How to get page uid in userfunc (localconf.php!) to be used in pageTSconfig condition?

[Roland Waldner]

I coded a userFunc in localconf.php to be used in pageTSconfig 
conditions to improve the BE experience for editors.

Is there a possibility to get the page uid (or even better the rootline) 
of the page the backend user is currently editing?

should work on:
- editing page properties
- column view of page
- creating new content element
- modifying content element

…unfortunatelly e.g. t3lib_div::_GET('id') does only work on column view.

maybe there is something useful in $GLOBALS? (i don't know how to debug 
$GLOBALS in localconf.php)