Symfony 4: Dotenv::populate returns none

Question

I am trying to run a Symfony4 app on production and I am getting the following error:

Uncaught TypeError: Return value of Symfony\\Component\\Dotenv\\Dotenv::populate() 
must be an instance of Symfony\\Component\\Dotenv\\void, 
none returned in /var/www/html/vendor/symfony/dotenv/Dotenv.php:95
Stack trace:
#0 /var/www/html/vendor/symfony/dotenv/Dotenv.php(57): 
    Symfony\\Component\\Dotenv\\Dotenv->populate(Array)
#1 /var/www/html/public/index.php(12): 
    Symfony\\Component\\Dotenv\\Dotenv->load('/var/www/html/s...')
#2 {main}
    thrown in /var/www/html/vendor/symfony/dotenv/Dotenv.php on line 95

On local the app is running fine. Once it moves to production, it breaks.

Any idea why this might be happening?

Answer 1

And is production running PHP5.x, or 7.0? The void return type is only available/reserved from PHP 7.1, and so it would think it could be a class in the same namespace - which does not exist either. Symfony 4 requires PHP 7.1.3