Validate an array of uploaded files laravel 5.1

I'm sorry for my english ) I have a problem - i need to validate an array of uploaded files. I want to check if each element of this array is image. I wrote custom validation rule, but i get error message "Call to a member function get() on array" In AppServiceProvider.php i wrote this code:

Validator::extend('images', function($attribute, $images, $parameters, $validator) {
            if (is_array($images)) {
                foreach ($images as $image) {
                    if (!exif_imagetype($image)) {
                        return false;
                    }
                }
                return true;
            } else {
                return exif_imagetype($images);
            }
        }); 

How can i do it? I want to use it like usual laravel rule in Request. Like this

public function rules()
    {
        return [
            'name' => 'required',
            'category_id' => 'required|integer',
            'images' => 'images',
            'content' => 'required',
            'chars' => 'required',
            'title' => 'required'
        ];
    }

via Chebli Mohamed