Facebook App to publish on users' walls?

The idea is quite simple, and a lot of codes exist on stackoverflow. I am just surprised I can’t find any ready-to-use scripts.

PHP script simply to post on users’ walls on Facebook.

When they visit the site they are asked to grant permission and when the token is provided and stored, I can send any post which will appear on all users’ walls.

Sample of the back-end:

Any suggestions? Thanks!