PHP & MySQL: mysqli_num_rows() expects parameter 1 to be mysqli_result, boolean given [duplicate]

$dbc is returning false. Your query has an error in it:

SELECT users.*, profile.* --You do not join with profile anywhere.
                                 FROM users 
                                 INNER JOIN contact_info 
                                 ON contact_info.user_id = users.user_id 
                                 WHERE users.user_id=3");

The fix for this in general has been described by Raveren.