[Admin]

Sorry, my bad.
I forgot to specify the table before the userid field:

// get newest member
$getnewestusers=$DB_site->query_first("SELECT user.userid,username,field9 FROM user LEFT JOIN userfield USING (userid) WHERE user.userid=$numbersmembers[max]");
$newusername=$getnewestusers['username'];
$newuserid=$getnewestusers['userid'];
$newuserlocation=$getnewestusers[field9];