Five most important commands if your Laravel is not working as expected after 
some modifications in .env or database folder or because of any other modifications. 
Here is full explanation: https://www.youtube.com/watch?v=Q1ynDMC8UGg

php artisan config:clear
php artisan cache:clear
composer dump-autoload
php artisan view:clear
php artisan route:clear

After clearup, try "echo env('URL_BUILDER')"