Overtrue\Validation\Validator::sometimes PHP Method

    public function sometimes($attribute, $rules, callable $callback)
    {
        $payload = array_merge($this->data, $this->files);
        if (call_user_func($callback, $payload)) {
            foreach ((array) $attribute as $key) {
                $this->mergeRules($key, $rules);
            }
        }
    }