I have a mostly "static" web site with no server-side code and just a little JavaScript. Now I would like to add a contact form. I do not care how I get the contact form data (so just writing this data to a text file in the server will be ok).
What is the simplest solution for this problem? How do people usually handle this?
I believe I can add some server-side code (PHP or something) to handle the form (and write the form data to a file, for instance) but I would prefer a client-side solution.
Use an external tool, they are commonly referred to as "formmailer". You basically submit the form to their server, and they send the form contents via mail to you.
If you don't want that, you have to do something server-sided: Storing data on the server, without having a server side program that accepts the data from the client, is just not possible.
You could install CouchDB and interface that from Javascript :) Everyone could use that then, too :)
The most easy PHP script that stores POST data on your harddisk:
<?php file_put_contents('/path/to/file', serialize($_POST) . "\n", FILE_APPEND); ?>