Getting 403 error accessing .php file

I built a simple contact form using HTML, and I am posting it to a .php mailer I setup. I am getting a 403 forbidden access error when trying to access the php file.

I don’t see anyone else using php files with grav anywhere in the forums so I am expecting that this is a no no. I haven’t been successful in setting up the built in forms, and it seems like a very difficult method to setup a simple contact form.

Can we use php files with Grav? If so, why am I getting a 403 error when trying to access my php file? Every other file and directory (custom or otherwise) is working fine.