Try this :
$i = 0;
while($row = mysqli_fetch_array($result)) {
$posts['post_id'] = $row[$i]['post_id'];
$posts['post_title'] = $row[$i]['post_title'];
$posts['type'] = $row[$i]['type'];
$posts['author'] = $row[$i]['author'];
}
$i++;
}
print_r($posts);