How to use sometimes rule in Laravel 5 request class

Question

I have the following request class:

Answer 1

According to your comment

I want the rule valid_date to only run if the regex rule returns true. Otherwise the valid_date rule errors if the date isnt in the right format.

Validator::extend('valid_date', function($attribute, $value, $parameters)
    {
       \\use the regex here instead

        if (!preg_match('/[0-9]{2}\/[0-9]{2}\/[0-9]{4}/', $value)) return false; 


        $pieces = explode('/', $value);
        if(strpos($value, '/')===FALSE) {
            return false;
        } else {
            if(checkdate($pieces[1], $pieces[0], $pieces[2])) {
                return true;
            } else {
                return false;
            }
        }
    });


$validator = Validator::make($data, [
   'first_name' => 'required',
    'last_name' => 'required',
    'email'     => 'required|email|unique:users,email',
    'dob'       => 'required|valid_date',
    'mobile'    => 'required',
    'password'  => 'required|confirmed'
]);