Carbon\Traits\Units.php:69 code example

Example: Carbon\Traits\Units.php:69

Looks like the new warning in PHP 7.1

Probably you have an empty SESSION_LIFETIME in the .env which cause this 
warning by calling the addRealUnit($unit, $value = 1) with the $value = ""

Solution: Update the .env and set a value to SESSION_LIFETIME or remove the 
SESSION_LIFETIME and the problem should be solved.