'not_exists' rule for validator in laravel 5.0+ [Simple Solution!]

ValidatorServiceProvider.php

<?php namespace App\Providers;

use Illuminate\Validation\Factory as Validator;
use Illuminate\Support\ServiceProvider;

class ValidatorServiceProvider extends ServiceProvider
{

    /**
     * Bootstrap the application services.
     *
     * @param Validator $validator
     * @return void
     */
    public function boot(Validator $validator)
    {
        $validator->extend('not_exists', function ($attribute, $value, $parameters) use ($validator) {

            //this is opposite of using `exists` rule, so we use exists
            //but when it fails, it returns true! [simple solution!]

            $v = $validator->make(
                [
                    $attribute => $value
                ],
                [
                    $attribute => "exists:" . implode(",", $parameters)
                ]
            );

            return $v->fails();

        });
    }

    /**
     * Register the application services.
     *
     * @return void
     */
    public function register()
    {
        //
    }

}