My b2evolution Version: 1.9.x

<? $logged_in_users = array_keys($Sessions->_registered_Users);
if(in_array($admin_id, $logged_in_users)) {
$user = $user -1;
} ?>

Warning: array_keys() [function.array-keys]: The first argument should be an array in /home/alkha4/public_html/blog/addOns/visitors/users.php on line 43

Notice: Undefined variable: admin_id in /home/alkha4/public_html/blog/addOns/visitors/users.php on line 44

Warning: in_array() [function.in-array]: Wrong datatype for second argument in /home/alkha4/public_html/blog/addOns/visitors/users.php on line 44