Use django for one page on a website?
If all you wanted to do was create a static page (something simple that queries a database and displays results with no user input) then PHP would definitely be much easier. It's much, much, MUCH easier to deploy than web apps-- just drop your .php files in /var/www/html and you're set. Apache runs on anything.
Once you're in the realm of needing user accounts, management, etc. or possibly even expansion of scope in the future then Django becomes a more likely candidate. I love Django but deployment of Python/Ruby apps can be a major pain (if not impossible) depending on many factors in your target environment. It looks deceptively easy to get something running when you're using the built-in webserver where everything just works, but in production you may find your host doesn't offer (or you can't compile) mod_wsgi, only has mod_python (incompatible with modern Django), won't run nginx, can't use gunicorn, etc. 
Every cheap web host offers PHP support out of the box. If you want support for apps written in Python/Ruby, sometimes you need to pay for additional services (if not running a VPS or EC2 instance).
Basically, there are more factors involved than just the number of pages you intend to write. You really need to evaluate what you're buying into with either avenue.
I have a small app I would like to build as a project to learn more about web development. Its an app where people can register etc, and add information about themselves (database needed) and their location on a webmap (using leaflet library). The app will be a single page application that the user navigate to via a link on the site that today is already live. 
I got a comment from one i know not to use php. Since I am learning python I was thinking maybe to use that for the server side bits. Is it a good idea to use django or other python framework when it will only be used on a single page of the site, is it even possible (very green on this)? Or should i just stick to php for a project this size?
Any input would appreciated