How to post to users' facebook wall even if they are not on my app web page

Question

I have an application that can post to user's wall when they visit my application page. But there are too much apps that are posting to users' wall even if users are not visiting their application (Users only visit once and give required permissions). I want to post to users' wall when they are offline and far away from Facebook.
Can you suggest how can I do that.

I am using PHP sdk.

Answer 1

You can request a long lived token for 2 months

https://graph.facebook.com/oauth/access_token?             
    client_id=APP_ID&
    client_secret=APP_SECRET&
    grant_type=fb_exchange_token&
    fb_exchange_token=EXISTING_ACCESS_TOKEN 

see https://developers.facebook.com/roadmap/offline-access-removal/