Data validation - exotic characters

[Anon]

Hello Gurus!

I need to validate usernames - and living in Sweden I need to be able to handle the letters å,ä,ö,Å,Ä and Ö. How should I change the following code??? Its the A-Z part in the function strip_letters that needs to be changed...

function is_allletters ($text)
{
$Bad = strip_letters($text);
if(empty($Bad))
{
return true;
}

	return false;
}

function strip_letters ($text)
{
$Stripped = eregi_replace("([A-Z]+)","",$text);
return $Stripped;
}