Laravel Project is not working Lampp & Ubuntu 16.04

Question

I have install a laravel in a htdocs folder using following command. When I have start a project using artisan it not start.please review a things.

​sevenbits11@SBT-PC-11:/opt/lampp/htdocs$ sudo composer create-project laravel/laravel first-project --prefer-dist
sevenbits11@SBT-PC-11:/opt/lampp/htdocs/first-project$ php artisan serve
PHP Warning:  require(/opt/lampp/htdocs/first-project/vendor/autoload.php): failed to open stream: No such file or directory in /opt/lampp/htdocs/first-project/artisan on line 18
PHP Fatal error:  require(): Failed opening required '/opt/lampp/htdocs/first-project/vendor/autoload.php' (include_path='.:/usr/share/php') in /opt/lampp/htdocs/first-project/artisan on line 18

Updated After Applied solution

sudo php artisan serve
PHP Warning:  require(/opt/lampp/htdocs/first-project/vendor/autoload.php): failed to open stream: No such file or directory in /opt/lampp/htdocs/first-project/artisan on line 18
PHP Fatal error:  require(): Failed opening required '/opt/lampp/htdocs/first-project/vendor/autoload.php' (include_path='.:/usr/share/php') in /opt/lampp/htdocs/first-project/artisan on line 18

Answer 1

Install the following dependency:

sudo apt-get install php7.1-xml

You can try refer the issues here: PHP7 : install ext-dom issue