Facebook App share

i have wordpress news site and i need a facebook app to share posts to facebook user that will read news in my page. Example if someone read post in my page [login to view URL] he need to allow the app to see the post and if he allow app he will se the post and the post will be shared automatic to his facebook wall , so first user need to allow app and after that every news he read will be publish on his fb. i will chose the lower price