Register your App, get your token and choose your root-folder. Now you can view and copy your file to your webspace.
This couple of files use the PHP Dropbox a (wrapper)class to communicate with Dropbox.
PHP Dropbox is BSD licensed.
The class is well documented inline. If you use a decent IDE you'll see that each method is documented with PHPDoc. More documentation can be found on http://classes.verkoyen.eu/dropbox/docs.