function test() {
     global $pageinfo, $themes, $pagetheme, $pagename;

     echo "preloop";
     while (list($akey) = each($pageinfo)) {
           echo "inloop";
     }
     echo "postloop";
}

In the above example, $pageinfo and $themes are arrays of arrays while $pagetheme and $pagename are just strings.  In the above case, calling the function for the first time gives us preloop, inloop (many times) and postloop, which is fine.  However, calling it the second time right after the first, or a bit later, yields only preloop and postloop.