Overtrue\Validation\Validator::parseStringRule PHP Method

    protected function parseStringRule($rules)
    {
        $parameters = [];
        // The format for specifying validation rules and parameters follows an
        // easy {rule}:{parameters} formatting convention. For instance the
        // rule "Max:3" states that the value may only be three letters.
        if (strpos($rules, ':') !== false) {
            list($rules, $parameter) = explode(':', $rules, 2);
            $parameters = $this->parseParameters($rules, $parameter);
        }
        return [studly_case(trim($rules)), $parameters];
    }