Add OR Clause to addSearchCondition

$criteria->addSearchCondition('AuthAssignment.itemname', 'Staff');
$criteria->addSearchCondition('AuthAssignment.itemname', 'Waiter' , true , 'OR');
$criteria->addSearchCondition('AuthAssignment.itemname', 'Admin' , true , 'OR');
$criteria->addSearchCondition('AuthAssignment.itemname', 'Cashier' , true , 'OR');