FB Php-SDK api(“/me”) return array with “An unknown error occurred”-Collection of common programming errors

I’m having this error when I request the info of the user:

$user_info      =       array(
   "error_code" => 1,
   "error_msg" => "An unknown error occurred"

)

What can be? it only happens with some users of my app not with all.

Originally posted 2013-11-09 19:45:00.