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I have the lamp installed on ubuntu 16.04 with the phpmyadmin database. I made form and am trying to find out the htdocs folder to insert the files into. Where is the htpdocs folder? It says it is in the root in the opt folder, but here is nothing and in the www folder neither. Where is this httpdocs directory on ubuntu 16 with lamp? Another situation ... can I install xamp and have the lamp installed on the ubuntu 16.04 LTS version? Thank you.

Welcome back.

No. Please stay away from XAMPP, it installs things in non-standard locations and requires manual updates. Stick with the standard web server, database, and scripting langauges from the repositories and life will be much easier. It will also be easier to get help with the various packages.

If you have installed Apache2 on Ubuntu, then the default document root for the default Apache2 virtual host would be /var/www/html/ and the configuration files for any virtual hosts you have would be in /etc/apache2/sites-available/