Вот решение, которое я нашел, но ответ @ C2486 намного лучше.
$sendto_hikkou = Guest::where('mypage_id', $mypage)
->select(
\DB::raw('COUNT(IF( snd_to_hikkou_id = 1, snd_to_hikkou_id, NULL)) AS item1'),
\DB::raw('COUNT(IF( snd_to_hikkou_id = 2, snd_to_hikkou_id, NULL)) AS item2'),
\DB::raw('COUNT(IF( snd_to_hikkou_id = 3, snd_to_hikkou_id, NULL)) AS item3'),
)
->get();