Answers for "PHP Warning: require(/var/www/html/vendor/autoload.php): failed to open stream: No such file or directory in /var/www/html/artisan"

failed to open stream: No such file or directory in artisan on line 18

The error is due to missing vendor folder.
You just need to run `composer install` in the project directory which will 
create a folder named vendor which will have all composer libraries and 
`autoload.php` file.