Sum (of an array) validation in Laravel

ValidationServiceProvider.php

<?php

namespace App\Providers;

use Illuminate\Support\Facades\Validator;
use Illuminate\Support\ServiceProvider;
use InvalidArgumentException;

class ValidationServiceProvider extends ServiceProvider
{
    /**
     * Bootstrap the application services.
     *
     * @return void
     */
    public function boot()
    {
        Validator::extend('sum', function ($attribute, $value, $parameters) {
            if (count($parameters) !== 1) {
                throw new InvalidArgumentException('Validation rule sum requires exactly 1 parameter.');
            }

            return array_sum($value) >= $parameters[0];
        });
    }

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

Usage:

'field_name' => 'sum:1'

Validates that the sum of an array is greater than the specified value. Handy for validating an associative array of product IDs and quantities, and ensuring that the sum of quantities is greater than zero (i.e. on a checkout form submission).

Great. Thanks a lot!