check if webroot points to the public directory... this is probably it if you're seeing composer.json and other files in the listing

I guess that it could have been a number of things, but I looked into my error logs (Ubuntu)

/var/log/apache2/error.log

and saw this error:

PHP Parse error:  syntax error, unexpected 'yield' (T_YIELD), expecting '(' in /var/www/path/to/laravel/helpers.php on line 563

so I did a Google search.

There is a Laravel function called yield() that collides with a reserved name in PHP 5.5 that was not in PHP 5.4. It so happens that my old server had PHP 5.4.

Found this which helped me to find all instances of 'yield()' in Laravel and change to '_yield()'. Problem solved!