@WhatIf and also "like" the official page on Facebook). They (CBS Films) did post that fans would unlock the official poster for What If when their Twitter page would have 500 followers.
The message was also shared on Daniel's official Google+ page with the following message:
And ofcourse via this site's Twitter & Facebook and well now they reached 500+ followers, so here's the poster (the tweet) with the text ".What If...being friends has its benefits?" :"Hi Everyone! Head over and follow @WhatIf on twitter. We need your help to unlock the world premiere of the OFFICIAL POSTER for the film!"- Dan
#Exclusive first look at the NEW POSTER for @WhatIf! #DanielRadcliffe @zoeinthecities #ThanksFansThe Google+ link at this page is Dan's post shared via our own Google+ page