Description: ------------ I try make my feedback form. That form have two fields: phone and e-mail. No one of them is not required, but user must fill one of them. If user leave emty both, then error: "u must fill phone _OR_ mail". I try addRule() to one of the formElement and validate by my callback function, BUT: "If the element is empty, no validation rules other than required are checked for it. This means that empty element can be invalid only when it is required. " Becouse both fields is empty, my callback rule doesn't checked and form is valid.

Have a look at the builtin-rules.php example file, it contains an example of that. You have to use the 'empty' rule and add rules using and_() or or_()