Denk niet dat het uitvoerbaar is zonder Eloquent.
Je kunt de primitieve route volgen:
$results = DB:table('posts')
->leftJoin('comments', 'posts.id', '=', 'comments.post_id')
->select('posts.*', 'comments.*', 'comments.id as comments_id')
->get();
foreach($results as &$result)
{
$result['comment'] = [
'id' => $result['comment_id'],
'comment' => $result['comment'],
'comment_author' => $result['comment_author']
];
unset($result['comment_author'], $result['comment_id']);
}