I am hosting my first webserver ever. I got myself a ubuntu based vserver and installes plesk and joomla.
Stupid question, but I wanted to create a form and and handle the input with a post.php file with a POST-method. But I have no clue where to place it on my server. Right now it is just in /var/www/vhosts/[MY WEBSITE.DE]/httpdocs/post.php, but this might be wrong.
Is there a specific file that I have to change or do I have to place my php-files in a specific directory? This question might be so stupid, I couldn't even find an answer on Google :D
Well, you can place your own code anywhere in the directory that plesk is using for your website. In your case : /var/www/vhosts/[MY WEBSITE.DE]/httpdocs/.
It is then your job to use that in your code where needed (I assume you have a form of some sort and that's why you are talking about a "post method", you just need to point that form to your whatever.php page you uploaded).
Please use FTP/your website username to upload your code into your website directory and not the root user or you'll end up with permission issues and nothing will correctly work.
A good start would be Getting Started with Managing Websites in Plesk and Option A. Upload Content