Query

$users = [];
$sql = "SELECT * FROM users ORDER BY id DESC LIMIT 0, 10";
$result = $mysqli->query($sql);
while ($row = $result->fetch_assoc()) {
    $users[] = $row;
}

$sql = "SELECT * FROM categories";
$result = $mysqli->query($sql);
$data = $result->fetch_all(MYSQLI_ASSOC);