<?php
header('Content-type: application/json');
$db = new mysqli('localhost', 'root', '', 'test');
$db->query('SET NAMES utf8');

$users = $comments = $result = array();

$query = $db->query('SELECT * FROM user');
while ($row = $query->fetch_object()) {
    $users[$row->id] = $row;
}

$query = $db->query('SELECT * FROM comment');
while ($row = $query->fetch_object()) {
    if (isset($comments[$row->user_id])) {
        $comments[$row->user_id][] = $row;
    } else {
        $comments[$row->user_id] = array($row);
    }
}

foreach ($users as $row) {
    $result[] = array(
        'user_id' => $row->id,
        'bot_name' => $row->displayname,
        'isActive' => $row->status,
        'children' => (isset($comments[$row->id]) ? $comments[$row->id] : array())
    );
}

exit(json_encode($result, JSON_NUMERIC_CHECK));