This post will show you how to sync all of your Facebook contacts details with the contacts in your iPhones addressbook.
It will only add the information that your Facebook contacts have allowed to be synced, so if bob or joe don’t want you having their new cell number or email address then this won’t help.
It will add entries to your addressbook for people that you have on Facebook that don’t already exist!!
login to the official Facebook app for iPhone.
Tap the three bars thing in the top left
Click on the share icon in the top right
Click ‘sync contacts’
Pick the syncing options you require.