Laravel 5.1 required_if验证不适用于数组

Question

I have the following array input fields. They are optional fields, however I want to use the required_if validation rule so that if the user enters a question they must select an expected answer as well. If user selects an expected answer then they should also include a question.

<input type="text" name="questions[0][question_text]">
@if ($errors->has('questions.0.question_text')) {{ $errors->first('questions.0.question_text') }} @endif

<select name="questions[0][expected_answer]">
    <option value="">Please Select</option>
    <option selected="selected" value="true">Yes</option>
    <option value="false">No</option>
</select>
@if ($errors->has('questions.0.expected_answer')) {{ $errors->first('questions.0.expected_answer') }} @endif

I've tried the following but it doesn't work:

 'questions.0.question_text' => 'required_if:questions.0.expected_answer,true,false',
 'questions.0.expected_answer' => 'required_with:questions.0.question_text'