ValidationServiceProvider.php

<?php namespace App\Providers;

use Illuminate\Contracts\Validation\Factory;
use Illuminate\Validation\ValidationServiceProvider as ServiceProvider;

class ValidationServiceProvider extends ServiceProvider
{
    protected $extendValidators = [
      //some validators name there
    ];

    /**
     * Register the service provider.
     *
     * @return void
     */
    public function register()
    {
        parent::register();

        $this->extendValidation();
    }

    /**
     * Extend validator factory.
     */
    protected function extendValidation()
    {
        $provider = $this;

        $this->app->extend('validator', function (Factory $validator) use ($provider) {
            foreach ($provider->extendValidators as $validatorName) {
              $validator->extend($validatorName, $provider->getValidatorCallback($validatorName));
            }

            return $validator;
        });
    }

    /**
     * Get validator function.
     *
     * @param string $validatorName
     * @return callable
     */
    public function getValidatorCallback(array $validatorName)
    {
        $validator = [$this, camel_case('validate_' . $validatorName)]

        return function () use ($validator) {
            return call_user_func_array($validator, func_get_args());
        };
    }
  
  //some validator functions there
  //public function validateSome($attribute, $values, $parameters){}
}