I have an array item with a French accent ([WIPDescription] => Recette Soupe à lOignon Sans Boeuf US). The data is being properly pulled from the database (mysql).
I found this to be the easiest way to deal with it
echo json_encode($array, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
JSON_PRETTY_PRINT - makes is readable
JSON_UNESCAPED_UNICODE - encodes characters correctly
JSON_UNESCAPED_SLASHES - gets rid of escape slash '\'
also notice that these option are separated by a pipe '|'