How i Download all files from the app folder into a specific folder on my server

It looks like your system doesn't have readline installed, or it isn't available to your app for some reason. That line of code prompts the user to enter the authorization code they receive from the Dropbox Web site.

That means you just need to install readline (or debug why it's not available to your app) or replace readline with whatever function is available on your platform for accepting input from the user, though that may be specific to your platform so I can't say off hand what the right answer for your system is. For example, here's a post about this for Ubuntu:

http://askubuntu.com/questions/182989/how-to-solve-fatal-error-call-to-undefined-function-readline-readline-librar